Preoperative cardiac management of patients undergoing non cardiac surgery

The estimation of an individual patient's "resistance" to major surgery has become an complex matter. Clinical parameters allow risk stratification in a large number of patients who are about to undergo noncardiac surgery. Low risk patients can be "cleared" for surgery. Moderate risk patients should undergo further testing. Exercise testing and pharmacological stress testing with myocardial perfusion imaging can refine risk estimation in these patients. This risk stratification is well backed by scientific data, although most of it is derived from studies in the same very high risk population, i.e. patients scheduled for vascular surgery. Less hard evidence exists when it comes to the management of the high-risk patient. Coronary bypass surgery should probably be reserved for those in whom additional indications for this procedure exist. The perioperative use of beta-blockers can possibly reduce operative risk. Data on perioperative monitoring and anesthetic technique are not yet convincing. The relative merits of various perioperative management strategies will remain uncertain until randomised trials are performed to evaluate the alternatives systematically.     

Perioperative cardiac evaluation for noncardiac surgery noninvasive cardiac testing

Prognostic risk stratification to identify perioperative and long-term cardiac risk in selected patients undergoing noncardiac surgery is part of good clinical practice. Exercise variables associated with significant increased risk include poor functional capacity (eg, <4 metabolic equivalents), marked exercise-induced ST segment shift or angina at low workloads, and inability to increase or actually decrease systolic blood pressure with progressive exercise. Approximately 40% of patients tested before peripheral vascular surgery will have an abnormal exercise electrocardiogram (ECG). The predictive value for a perioperative event, ie, death or myocardial infarction, ranges from 5% to 25% for a positive test and 90% to 95% for a negative test. Whereas exercise cardiac imaging is the modality of choice in patients with a noninterpretable exercise ECG, pharmacological stress imaging should be used in the 30% to 50% of patients who require perioperative noninvasive risk stratification and are unable to perform an adequate level of exercise to test cardiac reserve. Myocardial perfusion variables predictive of increased cardiac events include severity of the perfusion defect, number of reversible defects, extent of fixed and reversible defects, increased lung uptake of thallium-201, and marked ST segment changes associated with angina during the test. The reported sensitivity and specificity of dobutamine-induced echocardiographic wall motion abnormalities in patients with peripheral vascular disease is similar to myocardial perfusion scintigraphy, but the confidence limits are wider due to the smaller sample size in these more recent studies. In conclusion, noninvasive cardiac testing should be used selectively in patients undergoing noncardiac surgery; the results provide useful estimates of short- and long-term risk of cardiac events, and the magnitude of abnormal response on noninvasive testing should be used to formulate decisions regarding the need for coronary angiography and subsequent revascularization.     

Sudden cardiac death--preventable--reversible

SCD is defined as unexpected death due to cardiac causes that occurs within 1 hour of acute symptoms. SCD can be reversed with the use of an ICD. These devices now can be implanted by catheter techniques, obviating thoracotomy. SCD is preventable. The incidence of SCD can be significantly reduced by addressing the fundamental pathophysiology of SCD, which primarily is CAD. Our combined and aggressive implementation of preventive regimens to reduce the risk of cardiac events will save lives. These measures include diet, weight reduction, smoking cessation, regular exercise, and therapeutic drugs. Amiodarone, although effective in preventing lethal ventricular arrhythmias, has not matched the long-term results of the ICD in the successful management of SCD.     

Mechanical cardiac assistance

In neuropsychological vulnerability research the visual backward masking task, the Span of Apprehension, the degraded stimulus Continuous Performance Test (dsCPT), and the Wisconsin Card Sorting Test have been described as putative indicators for the predisposition to develop negative (schizophrenic) symptoms. The present study assesses the stability of the association between neuropsychological tests and negative symptoms by examining clinically improved patients. The interdependence between the four cognitive measures and clinical symptomatology was examined in 31 patients with DSM III-R and ICD-10 schizophrenia suffering predominantly from negative symptoms. Backward masking performance was related to affective flattening and anxiety-depression. False alarm rate on dsCPT was associated positively with affective flattening and hallucinations, and negatively with avolition. Card sorting preseverative errors correlated negatively with anhedonia, non-preservative errors correlated positively with avolition. Correlations notwithstanding, the data provide evidence in support of the relative independence of neuropsychological functions and negative symptoms in clinically improved schizophrenics.     

Preoperative cardiac evaluation

Four cases (3 children and one adolescent) are presented in which Parinaud's syndrome developed in the course of progressive non-tumorous hydrocephalus. The vertical gaze palsy completely disappeared in all cases some days after raised intracranial pressure had been successfully treated. Neuroradiological findings indicate that Parinaud's syndrome can be elicited by a dorsal midbrain compression due to a markedly dilated suprapineal recess. Other contributing factors as distortion and compression of distal branches of the posterior cerebral artery in the cisterna ambiens region and an axial caudal displacement of the oral brain stem may be involved. According to the few cases published in the literature, the vertical gaze palsy seems to occur predominantly in benign connatal aqueduct stenosis and may then be regarded as a relatively early symptom of decompensating hydrocephalic intracranial pressure.     

Permanent cardiac pacing

Supraventricular tachycardias generally present with narrow QRS complexes and are quite commonly seen in the emergency department. Regular narrow QRS complex tachycardias occur in all age groups and may be associated with minimal symptoms, such as palpitations, or, present with hemodynamic compromise resulting in syncope. While history and physical examination are indispensable, they usually do not lead to a definitive diagnosis. The diagnosis is made by careful analysis of the 12-lead ECG. Therapy is based on hemodynamic assessment and understanding of the tachycardia mechanism.     

Clinical utility of cardiac troponin I and cardiac troponin T measurements

The measurement of CK-MB remains the test of choice for confirmation or exclusion of AMI and probably will remain the test of choice for routine diagnosis in the near future. Nowadays determination of cardiac troponin T (cTnT) and cardiac troponin I (cTnI) as a method relatively expensive and time-consuming should be restricted to clinical settings that really require their high specificity.     

Normalization of cardiac structure and function after regression of cardiac hypertrophy

Previous studies have shown regression of left ventricular hypertrophy after pharmacologic treatment of hypertensive patients; however, the impact of regression of left ventricular hypertrophy on systolic function and on left and right ventricular diastolic function remains controversial and is difficult to assess because previous studies have not included concurrently studied age-matched control groups. Left ventricular mass, systolic function, and left and right ventricular diastolic function were assessed in 27 hypertensive patients, aged 43 +/- 6 years, by echocardiographic and Doppler studies before and 1, 3, 5, and 7 months after treatment. Left ventricular mass and ventricular function were concurrently evaluated in 27 age-matched normotensive subjects. Treatment with antihypertensive agents resulted in a significant (p < 0.001) reduction in diastolic blood pressure of 15 mmHg, measured at 1 month and sustained throughout the study. In response to hemodynamic unloading, left ventricular mass index decreased from 129 +/- 30 gm/m2 at baseline to 105 +/- 26 (p < 0.05) and 88 +/- 14 gm/m2 (p < 0.05) at 1 and 3 months of treatment, respectively, and remained unchanged over the subsequent 4 months. After 3 months of treatment, left ventricular mass index was similar in treated hypertensive and control subjects. Systolic function, assessed in terms of the relationship between shortening fraction and end-systolic wall stress, was unchanged throughout the treatment period and was no different from that in control subjects. However, patients with an initially depressed shortening fraction experienced a greater increase in shortening fraction during treatment compared to those with an initially normal shortening fraction (11% +/- 4% vs 5% +/- 5%, p < 0.01) and showed an improvement in the relationship between shortening fraction and end-systolic wall stress during treatment. Ventricular filling dynamics improved during the first 3 months of treatment, after which they were unchanged. Ventricular filling dynamics were similar in treated hypertensive patients and control subjects. In conclusion, sustained hemodynamic unloading of the left ventricle results in normalization of left ventricular mass, systolic function, and left and right ventricular diastolic filling dynamics, compared to those in age-matched control subjects.     

High cardiac output hypertensions

Hyperkinetic circulation, as it is related to the clinical hypertensive diseases, is defined and its implications interpreted. These pathophysiological considerations have an important bearing in understanding the pressor mechanisms underlying hypertension and the application of therapy. Another very important consideration is the value of elucidating the mechanisms for the hyperdynamic circulation, for with a clearer understanding of these, we shall come closer to an explanation of the pathogenesis of hypertension.