Quantitation of global and regional left ventricular function by cine magnetic resonance imaging during dobutamine stress in normal human subjects

Magnetic resonance imaging (MRI) provides high-resolution images of the heart. However, physical exercise during MRI is difficult due to space restriction and motion artefacts. To evaluate the feasibility of MRI during stress conditions, dobutamine was used as an alternative to exercise. Haemodynamics, ventricular volumes and wall thickening were measured at rest and during peak dobutamine infusion (15 micrograms.kg-1 x min-1) in 23 normal human subjects. To calculate left ventricular volumes, eight short-axis views were obtained encompassing the left ventricle from base to apex. At six levels, percent systolic wall thickening (%WTh) was measured in 18 segments (20 degrees intervals). Heart rate, systolic and diastolic blood pressures, stroke index, cardiac output and left ventricular ejection fraction increased significantly during dobutamine infusion (all P values < 0.001). In addition, %WTh increased significantly (P < 0.001) during dobutamine compared to the control state at all levels except in the apical and low-left ventricular levels. Both in control conditions and during dobutamine, segmental wall motion analysis showed the highest %WTh at the posterolateral area and the lowest %WTh at the septal region (P < 0.05). MRI clearly identifies wall motion dynamics and provides calculations of segmental wall thickening and haemodynamic parameters. Dobutamine is a useful stress agent by virtue of its safety, operator control and its effects which resemble physical exercise.     

Global phylogeography of the ridley sea turtles (Lepidochelys spp.) as inferred from mitochondrial DNA sequences

BACKGROUND: The cardiovascular applications of magnetic resonance (MR) techniques in coronary artery disease have increased considerably in recent years. Technical advantages of MR imaging are the excellent spatial resolution, the characterization of myocardial tissue, and the potential for three-dimensional imaging. These characteristics allow the accurate assessment of left ventricular mass and volume, the differentiation of infarcted from normal tissue, and the determination of systolic wall thickening and regional wall motion abnormalities. METHODS: In addition to the conventionally used spin-echo and cine-echo techniques, newer techniques such as myocardial tagging, ultrafast MR imaging and MR coronary angiography have been developed. These newer techniques allow a more accurate assessment of ventricular function (tagging), myocardial perfusion (ultrafast imaging), and evaluation of stenosis severity (MR coronary angiography). Particularly early detection and flow assessment of stenosed coronary arteries and bypasses by MR angiography would constitute a major breakthrough in cardiovascular MR imaging. Apart from the MR imaging techniques, cardiac metabolism may be well assessed using MR spectroscopy. This provides unique information on the metabolic behaviour of the myocardium under conditions stress-induced ischemia. However, the definite niche of cardiac MR spectroscopy has still to be settled. CONCLUSION: Currently, MR techniques allow the evaluation of anatomy and function (accepted use), perfusion and viability (development phase), and coronary angiography (experimental phase). A particular strength of MR imaging is that one single MR test may encompass cardiac anatomy, perfusion, function, metabolism and coronary angiography. The replacement of multiple diagnostic tests with one MR test may have major effects on cardiovascular healthcare economics and would outweight the cost inherent to the MR angiography procedure.     

Intraoperative transesophageal echocardiography for detection of myocardial ischemia

Preoperative myocardial ischemia seems to be a predictor of poor outcome when detected by electrocardiography, pulmonary capillary wedge/pressure measurement and echocardiography. It could be demonstrated, that regional wall motion abnormalities appear earlier and are more sensitive signs of myocardial ischemia than the ECG. Using intraoperative epicardial and transesophageal echocardiography, high quality 2-d echocardiographic images of the heart can be recorded. For monitoring of left ventricular function and wall motion the transesophageal approach is most often used. By the transesophageal approach the left ventricle can be scanned in the long axis and by the transgastric approach in cross sections. They correspond to the apical four-chamber and left parasternal cross sectional imaging of the heart. Using the transgastric approach in the papillary short axis view all segments representing the three coronary arteries can be imaged. Recording in this position have been found to be highly reproducible. Only localized ischemia of the apex of the ventricle may be missed. Methologically the rotation and translocation of the heart remain a problem using the cross section images of the heart. But the left ventricular papillary muscles and the septal-right ventricular boarders can be used as land marks. Wall motion is scored in five grades. In addition to the semiquantitative analysis also a quantitative calculation using computers is possible. Using the midd papillary short axis view in nearly 120 intraoperative transesophageal echocardiograms since 1989 analysis of the systolic wall thickening was possible in 73% of the patients. According to the literature review 87% of the patients undergoing coronary bypass surgery or non-cardiac surgery have signs of preoperative ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)     

Noninvasive stress testing of myocardial ischemia: comparison of GRE-MRI perfusion and wall motion analysis to 99 mTc-MIBI-SPECT, relation to coronary angiography

In the evaluation of ischemic heart disease only MR imaging seems to have the potential to assess myocardial perfusion, function, and coronary morphology on a single instrument. The aim of this study was to assess the feasibility of a stress test with dipyridamole (0. 56 mg/kg) to analyze myocardial perfusion by Gd first-pass enhancement in ultrafast gradient-recalled-echo MRI (perf-MRI), and wall motion by cine gradient-recalled-echo MRI (Cine-MRI) in one imaging session. Twelve patients underwent complete rest and stress studies; satisfactory MR images were acquired in 10 patients. By 99 mTc-MIBI-SPECT sensitivities to detect ischemic segments were 66.7 % with Perf-MRI, 80.0 % with WM-MRI and 86.7 % for Perf-WM-MRI (Perf-MRI vs Perf-WM-MRI; p = 0.03). Scar was equally detected with a sensitivity of 91.6 % with either MRI technique. Thus, Perf-Cine-MRI provides complementary information for the management of ischemic heart disease and has a higher sensitivity than Perf-MRI alone.     

Quantitative two-dimensional echocardiographic assessment of regional wall motion during transient ischemia and reperfusion in the rat

Nonlethal myocardial ischemia produces profound and long-lasting effects on regional ventricular function and metabolism (myocardial stunning) and protects against myocardial infarction from subsequent prolonged ischemia (ischemic preconditioning). Two-dimensional echocardiography (2DE) is an essential tool for quantitative analysis of regional and global left ventricular (LV) function during myocardial ischemia and reperfusion and the study of these phenomena. However, the inability to perform 2DE in the open-chest rat heart has seriously limited the use of this model. To investigate the effect of transient coronary occlusion on segmental wall motion and LV geometry, we employed a 20 MHz intravascular ultrasound catheter placed on the epicardial surface of the rat heart (n = 15) to yield 2DE images suitable for quantitative analysis. Three 2-minute left coronary occlusions were made, separated by 5 minutes of reperfusion, with imaging during occlusion and at 5 and 60 minutes of reperfusion. Ischemic and nonischemic wall thicknesses, LV cross-sectional area, estimated LV volume, and the fractional changes of these parameters were measured. In eight animals these values were also compared with necropsy measurements of wall thickness, LV cross-sectional area, and volume. LV and right ventricular structures were well visualized in short-axis cross-sectional images in all animals, and images suitable for quantitative analysis were obtained in 92% of the periods. Coronary occlusion caused immediate, marked LV cavitary expansion, which rapidly returned to normal by 5 minutes of reperfusion. Active systolic thickening of the anterior wall at baseline (47% +/- 3%) became passive thinning during occlusion (-6% +/- 2%) and recovered partially, to 30% +/- 3% at 5 minutes of reperfusion and 42% +/- 4% at 60 minutes (p < 0.0005 at 5 minutes of reperfusion vs baseline; p not significant at 60 minutes). Recovery of thickening after 5 minutes of reperfusion was not different after the first versus third occlusion (23% +/- 4% vs 30% +/- 3%; p = 0.19). Measurements made by 2DE correlated well with those made by necropsy, although wall thickness was slightly thicker by 2DE. We conclude that epicardial echocardiography with an intravascular ultrasound catheter provides quantifiable 2DE images in this model and yields accurate information on segmental wall thickening and ventricular geometry not available by other techniques. Left coronary occlusion in the rat is associated with marked global and segmental LV expansion, which rapidly reverses with reperfusion. Postischemic regional wall motion abnormalities are present after coronary occlusion as brief as 2 minutes and can be measured accurately. The effect of multiple brief occlusions is not cumulative.(ABSTRACT TRUNCATED AT 400 WORDS)     

Spectrum of coronary arterial spasm. Clinical, angiographic and myocardial metabolic experience in 29 cases

A relationship of coronary arterial spasm to variant angina pectoris, subendocardial ischemia, major ventricular arrhythmias and myocardial infarction has been demonstrated. In 29 patients, spasm was angiographically observed in normal-appearing coronary arteries (7 patients) as well as superimposed on various degrees of coronary atherosclerotic obstruction (22 patients). All patients experienced an atypical anginal syndrome;16 patients also experienced typical exertional angina. Coronary spasm appeared to be a major contributory factor in eight occurrences of myocardial infarction and in 11 incidents of ventricular tachycardia, ventricular fibrillation and heart block. Coronary spasm in the 29 cases was distributed in the following fashion: left main trunk, 6 cases; right main trunk, 12 cases; proximal left anterior descending artery, 13 cases; proximal circumflex artery, 1 case; distal left anterior descending artery, 1 case; and distal circumflex artery, 2 cases. In 5 cases coronary spasm was noted at multiple sites.     

Isolated congenital diverticulum of the left ventricle disclosed by ventricular tachycardia in a 72-year-old woman

A 72-year-old woman presented with poorly tolerated ventricular tachycardia reduced by intravenous amiodarone. The possibility of an ischaemic aetiology led us to perform coronary angiography. The coronary arteries were pathological. Left ventricular angiography revealed limited anterior hypokinesia and a large contractile apical pouch appended to the left ventricle by a long narrow neck. Despite the appearance suggestive of congenital left ventricular diverticulum (contractility, narrow neck) and because of the coexistence of ischaemic heart disease, we preferred to confirm the muscular nature of the diverticulum by myocardial thallium scintigraphy, which showed reversible decreased uptake in the anterior zone related to coronary artery disease, and confirmed the muscular nature of the diverticulum which showed normal thallium uptake. MRI clearly visualized the ventricular ectasia attached by a narrow neck to the rest the left ventricle. This long narrow neck indicated that this muscular diverticulum constituted a congenital diverticulum. The contribution of ultrasonography was limited by a poorly defined point during the examination. This congenital diverticulum, discover during adulthood, and previously asymptomatic, is a rare lesion, in the light of a review of the literature.     

AMO array multifocal versus monofocal intraocular lenses: long-term follow-up

BACKGROUND: Reperfusion therapy by primary coronary angioplasty has been shown to be beneficial for patients who present themselves up to 12 h after the onset of symptoms. However, the relationship between outcome and ischaemic time for patients who present relatively late after the onset of symptoms is still uncertain. The aim of this study was to investigate differences in patient characteristics, left ventricular function and clinical outcome among early (< 3 h), intermediate (3-6 h) and late (6-24 h) treated patients. METHODS AND RESULTS: From August 1990 until December 1995, we studied 496 patients who underwent primary coronary angioplasty for acute myocardial infarction. Patients who underwent reperfusion therapy between 6 and 24 h were more often of female gender and more often had diabetes. Primary coronary angioplasty was less successful with later time to reperfusion. Patients who had reperfusion therapy within 6 h showed recovery of left ventricular function at 6 months follow-up, while the left ventricular function of patients treated late had deteriorated. Reocclusion of the infarct-related vessel at follow-up coronary angiography was highest for patients with an ischaemic time of more than 6 h. They more often suffered a repeat myocardial infarction and had a significantly higher 6 months mortality. After adjustment for age, heart rate at presentation, gender, and the presence of diabetes by multi-variate analysis, ischaemic time remained an independent predictor of both left ventricular function recovery and 6 month mortality. CONCLUSIONS: The time from symptom onset to reperfusion is related to some baseline clinical characteristics, procedural success rate, left ventricular function and clinical outcome.     

Pharmacological and exercise stress echocardiography

Stress echocardiography (SE) is a recently developed technique to detect coronary artery disease and myocardial ischemia, and in increasing importance because several advantages are offered over nuclear perfusion imaging. Particularly, it is well established in acute coronary syndrome, that impaired left ventricular function is not always an irreversible process, and the information obtained using SE is useful for evaluating myocardial viability. Additionally, a progress in computer technology permits us to quantitatively assess the regional myocardial function during ischemia induced. Then, we introduced the feasibility of the pharmacological and exercise stress echocardiography for detecting myocardial ischemia and viability in this report.     

Value of radionuclide ventriculography and magnetic resonance imaging in the diagnosis of constrictive pericarditis

In suggestive clinical presentations, the diagnosis of constrictive pericarditis is confirmed by the haemodynamic findings of impaired ventricular filling (diastole). In this study of 15 patients with pure constrictive pericarditis, the diagnosis value of two non-invasive techniques little used in this indication until now was examined: radionuclide ventriculography (RV) and magnetic resonance imaging (MRI). The RV provides a "functional" diagnosis through the analysis of global and segmental left ventricular filling whilst MRI provides anatomical details of the pericardial thickening. Diastolic dysfunction on RV presented as an increased early diastolic filling time as shown by a shortening of the interval to third filling T1/3R (p < 0.0001), an increased peak diastolic E wave velocity (p < 0.01) and early onset (p < 0.001), increased one third (FR 1/3) and mid (FR 1/2) diastolic filling fractions (p < 0.01) and of the E wave velocity to maximal systolic ejection velocity (S) ration (p < 0.01). The atrial contribution to filling in end diastole decreased (NS). Asynchronous filling, shown by dispersion of the times of onset of segmental early diastolic E peak velocities (delta tE) or of one third diastolic filling delta T1/3R, decreased. Seven patients underwent MRI. Pericardial thickening was present in all patients. The pericardium varied from 6 to 14 mm thick (normal 2.5 +/- 0.7 mm), without any systolo-diastolic variation. The thickening was seen as a dark low intensity signal, indicating the fibro-calcific character of the tissues. Sagittal and coronal views clearly demonstrated the non-uniformity of pericardial thickening.(ABSTRACT TRUNCATED AT 250 WORDS)     

Growth hormone and heart performance. A novel mechanism of cardiac wall stress regulation in humans

OBJECTIVES: This study was designed to assess systolic wall stress and ventricular function in patients with deranged growth hormone secretion, in an attempt to elucidate the mechanisms of growth hormone interaction with heart performance. DESIGN: A case-control study. SUBJECTS: Thirty patients with active acromegaly, free of diabetes mellitus and coronary artery disease, and 25 subjects with congenital growth hormone deficiency were studied. Twelve growth hormone-deficient subjects were reevaluated after 12 months of recombinant human growth hormone therapy. Two groups of 30 normal subjects each were used as controls for the acromegalic and growth hormone-deficient patients, respectively. RESULTS: In the acromegalics, end-systolic wall stress was reduced (-20%; P < 0.01) due to ventricular wall thickening (+ 26%; P < 0.001), whereas cardiac output was significantly increased (+ 20%; P < 0.01). The velocity of fibre shortening was unchanged. In growth hormone-deficient subjects, end-systolic wall stress was markedly increased (+ 38%; P < 0.001) due to a significant reduction of ventricular wall thickness (- 28%; P < 0.001), whereas cardiac output was significantly decreased (-44%; P < 0.001). Replacement therapy with recombinant human growth hormone produced a partial correction of wall thickness and stress. Consequently, systolic performance and cardiac output improved significantly. CONCLUSION: This study demonstrates that growth hormone plays a role in the control of cardiac wall stress and performance through a mechanism mediated by the effect of growth hormone on myocardial tissue growth. The data may have therapeutic implications in cardiac diseases that lead to heart failure.     

Complete occlusion of the left main coronary artery and the importance of coronary collateral circulation

Study of four patients who survived complete occlusion of the left main coronary artery forms the basis of conclusions concerning the functional significance of coronary collateral circulation. Each of these patients had prominent collateral circulation from the right coronary artery. Global left ventricular function was maintained to the extent that congestive heart failure did not occur; the biplane ejection fraction was normal in the two patients where measurement was possible. The peak rate of systolic wall thickening by roentgen videometry in anterior left ventricular segments was normal in one patient and mild to moderately depressed in another. Experience with the patients described herein indicates that coronary collateral flow can provide critically needed circulatory support for the patient with coronary artery disease.     

Results of treatment of oral cavity mucosa cancer according to the data of the regional oncological clinic

A clinicofunctional examination of 72 patients with toxic diphtheria (mean age 36.8 +/- 7.1 years) has been made to study the course and outcome of diphtheria-related damage to the heart. It is shown that clinical symptoms of myocarditis became more prominent with growing severity of diphtheric infection and evidenced for diffuse affection of the left ventricle. EchoCG detected defective systolic function which in patients with unfavorable prognosis was associated with thickening of the myocardium and dilatation of the left ventricular chamber. 24-h Holter monitoring registered shifts in the end part of the ECG ventricular complex and various abnomalities in the heart rhythm. Focal myocardial lesions manifested with supraventricular and solitary ventricular extrasystoles. In diffuse myocarditis frequent ventricular extrasystoles prevailed. At autopsy, structural myocardial changes in toxic diphtheria were confirmed.     

Whither paediatric dentistry?

The noninvasive assessment of myocardial viability in patients with coronary artery disease and depressed left ventricular function has proven clinically useful for identifying those patients with ischemic cardiomyopathy who benefit most from coronary revascularization. Thallium-201 (201Tl) imaging at rest has been the radionuclide imaging technique most often utilized for distinguishing viable myocardium from scar. However, new technetium-99m (99mTc) perfusion agents such as 99mTc-sestamibi and 99mTc-tetrofosmin have emerged as alternatives to 201Tl for imaging of regional myocardial perfusion. Whether these new agents, which have better physical properties for imaging with a gamma camera than 201Tl, are valid for use in assessing myocardial viability is still uncertain. Recent clinical studies have demonstrated that these agents, when imaged using quantitative SPECT, can identify patients with myocardial hibernation who exhibit improved regional systolic function following revascularization. Experimental laboratory studies have shown that the uptake of 99mTc-sestamibi and 99mTc-tetrofosmin in ischemic myocardium is only slightly lower than the uptake of 201Tl. These 99mTc-labeled agents remain bound intracellularly in mitochondria of viable myocytes under conditions of myocardial stunning and short-term hibernation, producing severe myocardial asynergy. With respect to determination of viability, the inferior wall region is at times problematic since attenuation of 99mTc-sestamibi and 99mTc-tetrofosmin is greatest in this area. Demonstration of preserved systolic thickening on ECG-gated SPECT images is indicative of viability in the instance of decreased regional 99mTc counts due to attenuation and not scar. Administration of nitrates prior to tracer injection improves the sensitivity for identifying viable myocardial segments using rest imaging with 99mTc-sestamibi or 99mTc-tetrofosmin. Thus, it appears that the new 99mTc perfusion imaging agents can be successfully employed for the determination of myocardial viability in the setting of severe regional dysfunction and chronic coronary artery disease. The greater the myocardial uptake of these agents in the resting state, the greater the probability of improved systolic function after coronary revascularization.     

Vulvovaginal hematomas complicating delivery. Rationale for drainage of the hematoma cavity

Coronary atherosclerosis is a pathologic process that produces thickening of the walls of the coronary arteries to the point that flow through those vessels may be impaired. This study attempts to use transthoracic echocardiography to detect coronary atherosclerosis. Eighty-nine patients undergoing coronary angiography were examined with a broad-band ultrasonic transducer with a frequency between 3 and 5 MHz. A modified short axis examination was utilized to identify left main and proximal left anterior descending arteries. The examination was recorded digitally and displayed in a 32-cell, quad screen cine loop. Fifty-six of the 89 patients (63%) had obstructive coronary artery disease (CAD) (i.e, at least 1 vessel with 50% obstruction). There were 14 patients with CAD but no vessel had > or = 50% obstruction. Nineteen patients (21%) had angiographically normal arteries. The coronary echograms were judged qualitatively for brightness, uniformity, and persistence (defined as the ability to see segments of the artery walls in more frames than other segments). The length of the coronary artery visualized, the width of the left main coronary artery, and the width of the thickest segment of the coronary artery walls were quantitatively measured. More than 2 cm of the left coronary artery was seen in almost all patients. Segmental changes were noted in 52 of the 56 patients with obstructive CAD, 12 of the 14 patients with nonobstructive CAD, and 3 of the 19 patients with normal arteries. Persistence greatly enhanced the ability to judge the segmental changes. Forty-six patients with obstructive disease had wall thickness > or = 1.5 mm. Only 6 patients with nonobstructive coronary arteries had this wall thickness, and only 1 normal subject had thick walls. The ultrasonic findings were useful in predicting the presence or absence of coronary atherosclerosis to varying degrees of sensitivity and specificity based on the segmental findings and wall thickness measurements. The results of this study indicate that a transthoracic ultrasonic examination of the proximal left coronary artery could be a clinically valuable tool in the qualitative identification of coronary atherosclerosis.     

Impact of acute pulmonary rejection on cardiac function

BACKGROUND: Experiments were designed to define cardiac function in dogs with single lung allografts during acute rejection of the allografted lung. METHODS AND RESULTS: Left lungs were either autotransplanted (n = 4) or allotransplanted (n = 8) in adult male mongrel dogs. All allotransplanted animals were maintained on triple-drug immunosuppression (cyclosporine, azathioprine, and steroids) for 5 days after the operation. In 4 allotransplanted animals, treatment was discontinued, allowing the animals to reject (usually after a further 3 days; rejecting group); 4 other allotransplanted animals were maintained on immunosuppression for an additional 3 days (immunosuppressed group). Another group of dogs were not operated on but were maintained on the same immunosuppression as the rejecting group (controls). All experimental animals underwent fast computed tomographic scanning with measurement of left ventricular pressure and calculation of ventricular chamber volumes, cross-sectional areas of coronary arteries, myocardial perfusion, and intramyocardial blood volume. Neither cardiac output, left ventricular mass, left ventricular pressure, nor myocardial oxygen consumption was altered during acute rejection of lung allografts. However, left ventricular contractility (systolic elastance, Emax) and ejection fraction were depressed to approximately one half (P < .05) in acutely rejecting animals compared with other groups. The cross-sectional area of the coronary arteries was less in autotransplanted and allotransplanted treated animals than in animals that were not operated on. Cross-sectional area of the coronary arteries was decreased by an additional 30% in the rejecting group (P < .05). CONCLUSIONS: The results of this study indicate that acute rejection of a single lung allograft decreases cardiac performance and reduces diameter of coronary arteries in the recipient. Alterations of circulating humoral factors and activated leukocytes may contribute to these changes.     

Perfusion of ischemic myocardium during anesthesia with sevoflurane

BACKGROUND: Sevoflurane produces direct vasodilation of coronary arteries in vitro and decreases coronary vascular resistance in vivo, pharmacologic properties that may contribute to the development of "coronary steal." This investigation examined the effects of sevoflurane on the distribution of regional myocardial perfusion in chronically instrumented dogs with steal-prone coronary artery anatomy. METHODS: Dogs were chronically instrumented for measurement of aortic and left ventricular pressure, diastolic coronary blood flow velocity and subendocardial segment length. After recovery from surgery, dogs underwent repetitive, brief, left anterior descending coronary artery (LAD) occlusions via an implanted hydraulic vascular occluder to enhance collateral development. A progressive left circumflex coronary artery (LCCA) stenosis was also obtained using an ameroid constrictor. After development of LCCA stenosis, the LAD was totally occluded to produce a model of multivessel coronary artery disease. Systemic hemodynamics, regional contractile function and myocardial perfusion measured with radioactive microspheres were assessed in the conscious state and during sevoflurane anesthesia at 1.0 and 1.5 MAC with and without restoration of arterial blood pressure and heart rate to conscious levels. RESULTS: Total LAD occlusion with simultaneous LCCA stenosis increased heart rate, mean arterial pressure, left ventricular systolic and end-diastolic pressures, end-diastolic segment length, and rate-pressure product in conscious dogs. Subsequent administration of sevoflurane caused dose-related decreases in arterial pressure, left ventricular systolic pressure, double product, and peak rate of increase of left ventricular pressure at 50 mmHg. Perfusion of normal myocardium was unchanged during sevoflurane anesthesia. In contrast, sevoflurane caused dose-dependent decreases in blood flow to myocardium supplied by the stenotic LCCA, which returned to control levels after restoration of heart rate and arterial pressure. No reduction in collaterally derived blood flow to the occluded region was produced by 1.0 or 1.5 MAC sevoflurane. No redistribution of blood flow away from the occluded LAD region to normal or stenotic myocardium occurred during sevoflurane anesthesia. In fact, increases in the ratio of blood flow between occluded and normal zones or occluded and stenotic zones were observed in the subepicardium during 1.5 MAC sevoflurane with maintenance of the heart rate and arterial pressure at conscious levels. CONCLUSIONS: The results demonstrate that sevoflurane does not reduce or abnormally redistribute myocardial blood flow derived from coronary collateral vessels in a chronically instrumented canine model of multivessel coronary artery obstruction.     

Combined assessment of myocardial perfusion and left ventricular function with exercise technetium-99m sestamibi gated single-photon emission computed tomography can differentiate between ischemic and nonischemic dilated cardiomyopathy

The purpose of this study was to determine whether exercise technetium-99m sestamibi gated single-photon emission computed tomography (SPECT) accurately distinguishes between patients with ischemic cardiomyopathy and patients with nonischemic left ventricular systolic dysfunction. Noninvasive tests have previously failed to accurately separate patients with ischemic cardiomyopathy from those with nonischemic cardiomyopathy. Technetium-99m gated SPECT imaging offers advantages that have the potential to overcome the limitations of previous studies. Thirty-seven adults with a left ventricular ejection fraction < or = 35%, including 24 patients with nonischemic cardiomyopathy and 13 patients with ischemic cardiomyopathy, were prospectively evaluated using symptom-limited metabolic exercise treadmill testing with technetium-99m sestamibi gated SPECT imaging. Interpretation of myocardial perfusion and regional wall motion was performed, using a 17-segment model. Summed stress, rest, and reversibility perfusion defect scores were determined, and the variance of segmental wall motion scores was computed. Summed stress, rest, and reversibility perfusion defect scores were significantly lower in nonischemic cardiomyopathy patients, compared with those with ischemic cardiomyopathy (summed stress defect score: 6.9 +/- 3.8 vs 32.9 +/- 7.7, respectively, p <0.001). Variability in segmental wall motion was also significantly lower in patients with nonischemic cardiomyopathy compared with those with ischemic cardiomyopathy (variance: 0.3 +/- 0.3 vs 1.2 +/- 0.8, respectively, p <0.001). Thus, assessment of myocardial perfusion and regional ventricular function with exercise technetium-99m sestamibi gated SPECT imaging can reliably distinguish between patients with ischemic cardiomyopathy and patients with nonischemic dilated cardiomyopathy.     

Color-coded measures of myocardial velocity throughout the cardiac cycle by tissue Doppler imaging to quantify regional left ventricular function

TDI is a new echocardiographic technique that calculates and displays color-coded myocardial velocity on-line. To determine the feasibility of endocardial velocity throughout the cardiac cycle as a means to quantify regional function, 20 normal subjects aged 30 +/- 5 years and 12 patients with heart disease aged 62 +/- 17 years were studied with a prototype TDI system. TDI M-mode images were acquired by using a multicolored velocity map (display range, -30 to 30 mm/sec; temporal resolution, 90 Hz). Color-coded velocity data were then converted to numeric values off-line at 50 msec intervals. Posterior wall velocities throughout the cardiac cycle by TDI were closely correlated with velocity calculations from the first derivative of routine digitized M-mode tracings (group mean r = 0.88 +/- 0.03, SEE = 7.0 +/- 1.1 mm/sec). Anteroseptal TDI color-coded systolic velocity occurred 164 +/- 84 msec from the onset of the electrocardiographic QRS compared with 203 +/- 33 msec in the posterior wall (P < 0.05) in normal subjects, consistent with normal electrical activation. Significant differences in systolic and diastolic posterior wall TDI velocity data were observed in patients with hypokinetic or akinetic segments assessed by independent routine study when compared with normal controls. Calculated systolic and early diastolic posterior wall TDI indexes correlated significantly with percentage of wall thickening. Of abnormal anteroseptal segments, TDI systolic time velocity integrals were significantly different than normal and correlated with percentage of wall thickening. TDI has potential to quantitatively assess regional left ventricular function.     

Comparison of modalities to diagnose coronary artery disease

The purpose of this review is to compare several modalities available for detection of coronary artery disease (CAD). We compare the clinical history, rest/exercise electrocardiogram (ECG), rest/stress left ventricular (LV) function by radionuclide or echocardiographic methods, myocardial perfusion imaging (MPI) by single photon emission computed tomography (SPECT) or positron emission tomography (PET), contrast coronary angiography, magnetic resonance imaging (MRI), spectroscopy (MRS) and angiography (MRA), and ultrafast cine computed tomography (UFCT) to assess LV function, myocardial perfusion, and coronary calcification. We compare the modalities by answering six questions: (1) Does the modality provide unique clinical information? (2) What is the observer error? (3) What are sensitivities and specificities to detect CAD? (4) What patient selection criteria should be applied for each modality? (5) What incremental benefit is obtained from one modality versus another modality? and (6) Where do the modalities fit in the overall scheme of diagnostic testing for CAD? PET MPI appears to be the best noninvasive test for CAD, followed by SPECT thallium-201 and then dobutamine echocardiography. MRA and UFCT may soon play a larger role because they visualize the arteries. Contrast coronary angiography remains the gold standard despite its limitations. Exercise ECG is the least accurate test. The choice of tests critically depends on patient selection--based on clinical history, age, gender, and risk factors to estimate the pretest, clinical probability of CAD.