David G. Meyers

Mitral Valve Prolapse in Anorexia Nervosa

Excerpt Mitral valve prolapse occurs frequently in patients with anorexia nervosa (1, 2). We have confirmed this association and identified one of its causes. We examined 28 consecutive female pati...

The effect of baseline electrocardiographicabnormalities on the diagnostic accuracy of exercise-induced ST segment changes

Although exercise-induced ST segment depression is thought to be unreliable marker of myocardial ischemia in the presence of resting electrocardiographic changes, this conclusion is based on limited and disparate data from studies often lacking acceptable measures of ischemia. To determine the diagnostic accuracy of the ST segment response in a blinded prospective protocol, we compared ST deviation to thallium201 SPECT scintigraphy in 95 patients during exercise. Diagnostic accuracy was poor in the 95 patients with resting abnormalities: left bundle branch block (LBBB) = 70%, complete right bundle branch block (cRBBB) = 75%, incomplete right bundle branch block (incRBBB) = 79%, intraventricular conduction delay (IVCD) = 44%, left ventricular hypertrophy (LVH) = 59%, digitalis = 53%, compared with a diagnostic accuracy of 90% in 29 patients without resting changes. There were 20 false negative and 17 false positive ST segment responses. The extent and direction of resting ST deviation varied substantially and had no influence on diagnostic accuracy. The extent of change in ST deviation with exercise required for a positive response did not alter diagnostic accuracy: -1.0 mm = 61%, -1.5 mm = 63%, and -2.0 = 61%. While the location of regional ischemia did not influence the accuracy of ST segment analysis, a QRS duration less than 120 msec did improve diagnostic accuracy. Our data confirm that ST segment analysis with exercise testing is not reliable in patients with resting electrocardiographic abnormalities and demonstrates that accuracy is not improved by adjusting for either resting or exercise-induced ST segment changes or for location of the ischemic region.

The Antioxidant Vitamins: Impact on Atherosclerosis

Atherosclerosis, the great killer of Western society, probably is initiated when the balance of subendothelial lipoproteins and oxidation potential is upset. Oxidation products, especially oxidized low‐density lipoprotein, set into motion the cascading of numerous pathways, culminating in the fibrous atherosclerotic plaque. The natural antioxidant system includes enzymes and vitamins A, E, and C. The lipophilic vitamins A and E protect the fatty acid components of lipoproteins and membranes, and vitamin C functions in the aqueous phase both directly and by regenerating oxidized vitamin E. In animal models, the antioxidant vitamins protect lipids and prevent atherosclerosis. Population studies suggest an inverse relationship between atherosclerosis and vitamin levels. Several observational studies and some clinical trials have demonstrated that antioxidant vitamin supplements may prevent atherosclerosis. Although approximately 20% of the United States population regularly consumes vitamin supplements, often in high doses, the antiatherogenic benefits of antioxidant vitamins remain unproved by clinical trials, and the long‐term effects of megadose vitamins are yet undefined.

Relative survival benefits of risk factor modifications

E ditorials in The American Journal of Cardiology have long urged an aggressive approach to management of coronary risk factors. Roberts’ has pointed out that regression of atherosclerosis and reduction in coronary event rates are determined by the amount of lowering of plasma total cholesterol and low-density lipoprotein (LDL) cholesterol levels. Vogel2 subsequently called attention to the effectiveness of cholesterol lowering relative to coronary bypass grafting and angioplasty. This editorial will attempt to extend the arguments of those editorials by defining the relative survival benefits derived from screening and treatment of smoking, inactivity, elevated plasma total cholesterol (or LDL cholesterol), and hypertension, treated either singly or multiply. Table I lists the range of number of lives that would be saved over a 5-year period in a cohort with coronary artery disease when modifiable coronary risk factors are screened and identified abnormalities are treated. Calculations assume a stable 16% 5-year mortality rate as observed in several large cohorts with ages of 40 to 80 years (mean 53).3-7 The calculations utilize risk factor prevalence, decremental mortality rates taken from clinical trials of risk factor treatments, and patient compliance-success rates. Genest and co-workers,8 in a cross-sectional study of 321 men with coronary artery disease documented by coronary angiography, observed the prevalence of smoking (>lO cigarettes/day) to be 67%, of high-density lipoprotein (HDL) cholesterol ~35 mg/dl (either alone or in conjunction with other lipid abnormalities) to be 63% (a 40% prevalence has been noted in a similar cohort of outpatient veterans9), hypertension 41%, LDL cholesterol with >160 mg/dl26%, and of diabetes mellitus (definition not given) to be 12%. Activity levels and obesity were not surveyed. In the US population, the estimated prevalence of sedentary lifestyle is 58%.‘O The prevalence of inactivity in the subpopulation with atherosclerosis is likely higher. Large secondary prevention trials have recently defined the improvement in survival resulting from risk factor treatment. Cessation of smoking produces a 50% reduction in total mortality (range 20% to 90%), with particular potency immediately after myocardial infarction, as determined by long-term follow-up of selfselected cohorts.4Jj*“v’2 Reducing total cholesterol or LDL cholesterol results in a 30% reduction in total mortality and a 42% reduction in cardiovascular events. I3914 Using meta-analysis, O’Connor et all5 calculated that

Repolarization abnormalities in mitral valve prolapse

Inferolateral ST depression, T wave inversion, and QT prolongation have been frequently described in reports of largely symptomatic mitral valve prolapse (MVP) patients, but not in a recent population-based survey of mainly asymptomatic subjects with MVP. To learn if there is a relationship between these ECG changes and symptoms, physical findings or hemodynamic sequelae, we reviewed ECGs from 119 patients, ages 18 to 60 years who had MVP diagnosed by echocardiography. Seventy-four percent had symptoms characteristic of MVP. ST-T changes were found as frequently in asymptomatic patients (29%) as in those symptomatic (27%), and did not identify those with hemodynamic sequelae of MVP (apical systolic murmurs, Doppler-defined mitral regurgitation, or left atrial enlargement). QT prolongation was found more frequently in the symptomatic group (25% vs 10%) but did not predict syncope. When compared to the expected 0.9% prevalence of ST abnormalities in a normal population, ST-T changes and QT prolongation are indeed frequent in MVP, but are not useful in identifying clinically important subsets.

Mechanism of disappearance of S3 with maturation

S3 is generally audible in normal children and young adults but disappears with maturation. Disappearance of the physiologic S3 has been correlated with a decrease in the rate of early diastolic left ventricular filling and subsequent deceleration of inflow, possibly resulting from maturation-associated relative left ventricular hypertrophy.1 We examined the association of the disappearance of the physiologic S3 to changes in left ventricular diastolic function with aging.