Effect of depressed left ventricular function on hemodynamics of normal St. Jude Medical prosthesis in the aortic valve position.

To evaluate the effect of left ventricular (LV) dysfunction on Doppler-derived transprosthetic hemodynamic indexes in patients with normally functioning St. Jude aortic valve prostheses, 74 consecutive patients were studied. LV ejection fraction was assessed by using Simpson's biplane rule. The 34 patients with normal ejection fraction (greater than or equal to 0.51) (group A) generally had the highest values of peak (31 +/- 13 mm Hg) and mean (16 +/- 6 mm Hg) gradients, whereas 19 patients with moderate to severe reduction of ejection fraction (less than or equal to 0.31) (group C) had the lowest values (17 +/- 6 and 9 +/- 3 mm Hg, respectively) (p less than 0.05). Significant decreases (p less than 0.05) for acceleration and corrected (for heart rate) velocity time integral in group C were noted compared to group A, and group B (21 patients with mild to moderately reduced ejection fraction [0.50 to 0.32]). A significant inverse correlation for Doppler-derived peak and mean gradients and corrected velocity time integral was demonstrated with increasing aortic valve prosthetic sizes from 19 to 29 mm in group A patients (r = -0.41 to -0.71) but less so in group B or C. Thus, in addition to valve size, LV function should be considered an important factor in detecting prosthetic valvular flow characteristics and dysfunction. A normal derived velocity and gradient in patients with moderately to severely depressed LV function may not rule out significant valvular stenosis.

Role of exercise thallium 201 imaging in decision making.

This prospective study examined the impact of results of exercise thallium 201 imaging on the estimation of probability of coronary artery disease (CAD) and patient management among cardiologists and internists in our institution. Before exercise testing, the probability of CAD in the 100 patients enrolled in this study was considered low in 31, intermediate in 28, and high in 41 patients. The probability of CAD after exercise thallium imaging was different in four patients (10%) in the high group, 22 patients (79%) in the intermediate group, and three patients (10%) in the low group. Further, the results of exercise testing resulted in changes in patient management in 29 patients (71%) in the high group, 26 patients (93%) in the intermediate group, and 16 patients (52%) in the low group. Overall, the management changed in 71% of the patients. This change included changes in medications, physical activity, frequency of office visits, need for cardiac catheterization, and need for coronary arterial bypass grafting. Thus, exercise thallium imaging is useful in clinical decision making: the diagnostic certainty is improved in patients with intermediate pretest probability of CAD; and some degree of change in patient management is observed, even in patients in whom the probability of CAD is not altered.

The special problems of the patient with a valvular prosthesis.

In essence, patients who have valve replacement have one disease replaced by another. Neither the mechanical nor the tissue valves available at present are free of complications. These complications include hemodynamic and hematologic abnormalities, intrinsic valve malfunction, infective endocarditis, arrhythmias, and congestive heart failure. Of these disorders thrombosis, thromboembolism, hemorrhage from anticoagulants, and infective endocarditis are the most frequent. Careful followup and awareness of the various medical problems that may arise in this group of patients are mandatory.

Tracking of atrial flutter during DDD pacing: another form of pacemaker-mediated tachycardia.

Two patients who had DDD pacemakers inserted for symptomatic sick sinus syndrome developed sustained upper-rate limit pacing. It was demonstrated in these two patients that pacemaker-mediated tachycardia was due to tracking of atrial flutter. DDD pacemakers should be used with caution in patients with the sick sinus syndrome and associated atrial tachyarrhythmias. Medical treatment of recurrent atrial tachyarrhythmias may allow patients to remain in the DDD mode.

What is optimal drug therapy in angina pectoris?

The treatment of classic angina pectoris must be carefully individualized, taking into account factors such as age, degree of disability, anatomic location and extent of lesions, ventricular function, and psychologic makeup of the patient. In some instances, early coronary bypass surgery is indicated. In other cases, a trial with full medical therapy is indicated and, if successful, medical management should be continued with careful, ongoing monitoring of the clinical course. Medical treatment should be considered a failure only if maximal dosage of nitrates and beta blockers is attained without satisfactory control of symptoms. The advent of calcium-channel blockers appears to add a new dimension in the treatment of variant angina, and these drugs may be useful also in certain patients with fixed coronary lesions and concomitant coronary artery spasm.

Electrophysiologic testing: clinical applications.

Electrophysiologic studies can be used in evaluating a large number of arrhythmias and conduction disturbances. These tests are extremely useful in the diagnosis and treatment of sick sinus syndrome, paroxysmal supraventricular tachycardias, atrial flutter, and AV conduction abnormalities. The decision to implant a permanent pacemaker in patients with a history of syncope also may be aided by the results of electrophysiologic studies. Finally, electrophysiologic studies have been used in the diagnosis and treatment of recurrent sustained ventricular tachycardia and in the evaluation of survivors of cardiac arrest. It is in these last two areas that electrophysiologic testing may have its widest and most important applications.

Effects of thiopental on tension development, action potential, and exchange of calcium and potassium in rabbit ventricular myocardium.

Thiopental in concentrations of 28 and 227 mumoles/liter reduced the tension developed by isolated rabbit ventricular myocardium by 50 and 80%, respectively. The effect was rapid, reversible, and independent of heart rate. Thiopental (227 mumoles/liter) inhibited influx and efflux of potassium to the same extent, so that no net gain or loss occurred. Calcium influx and efflux were also reduced, but calcium was not displaced from the myocardium in association with the decline of tension. The maximum rate of depolarization of the action potential and the time to 50% repolarization were decreased, but resting membrane potential, amplitude, and time to 90% depolarization were unchanged. The negative inotropic effect of thiopental appears to be due to reduced availability of calcium to the myofibrils.

Left ventricular end-diastolic pressure response to atrial pacing in idiopathic mitral valve prolapse.

The response of several parameters of left ventricular function to right atrial pacing was compared in 21 patients with idiopathic mitral valve prolapse and 10 normal patients. An inability to appropriately lower left ventricular end-diastolic pressure with increasing rates was demonstrated in the mitral valve prolapse group. This abnormality was not related to mitral regurgitation or factors other than ventricular performance per se.

T-wave abnormalities of intermittent left bundle-branch block.

Ischemia is traditionally considered a cause of intermittent left bundle-branch block (LBBB), and some patients have right precordial T-wave inversion in the normally conducted beats. Clinical correlates of T-wave abnormalities were examined in 46 consecutive patients with intermittent LBBB. Thirty-three patients (72%) had at least transient right precordial (V-14) T-wave inversion suggesting ischemia in normally conducted beats. Seventeen such patients had no evidence of coronary heart disease, including five with normal arteriograms. During LBBB conduction, T-wave abnormalities (upright T-waves I, aVL, V5-6) were frequent (48%) and more common than among patients with permanent LBBB (p less than 0.005). The T-wave abnormalities during LBBB conduction occurred in the absence of coronary heart disease in nine patients, including two with normal arteriograms. Thus, right precordial T-wave inversion may result from recent LBBB itself, associated with T-wave abnormalities during the LBBB, in the absence of coronary artery disease.

Ventricular extrastimulation in the mitral valve prolapse syndrome. Evidence for ventricular reentry.

Fourteen patients with mitral valve prolapse and essentially normal coronary arteries were evaluated for ventricular arrhythmias, utilizing programmed ventricular extrastimulation. Three were symptomatic with ventricular tachyarrhythmias. Application of appropriately timed ventricular extrasystoles initiated the tachyarrhythmias in these three patients. The remaining eleven mitral prolapse patients were apparently free of tachycardias. Repetitive ectopic beats were not induced by extrastimulation in these eleven patients. The initiation of ventricular tachyarrhythmias by extrastimulation suggests a reentrant mechanism for the ventricular ectopy of mitral valve prolapse.

Electrophysiologic effects of hydralazine on sinoatrial function in patients with sick sinus node syndrome.

The electrophysiologic effects of hydralazine were evaluated in nine hypertensive patients with sinoatrial dysfunction. Intravenous hydralazine, 0.15 mg/kg, caused no significant reduction in arterial blood pressure. Yet this dose of hydralazine increased heart rate from 61.9 +/- 4.1 beats/min (mean +/- standard error of the mean) to 68.6 +/- 4.9 (P less than 0.001). Sinus nodal recovery time upon termination of atrial pacing shortened from 3,207 +/- 1,098 to 2,064 +/- 573 msec (P less than 0.05) and second escape cycles shortened as well (P less than 0.025). Acceleration of heart rate and abbreviation of recovery time did not closely correlate with change in blood pressure (r = 0.41 and 0.18, respectively). Junctional escape beats became more frequent and junctional escape time shortened from 2,525 +/- 692 to 1,705 +/- 382 msec (P less than 0.05). Sinoatrial conduction time tended to shorten, but a significant change was not observed. Atrial tachyarrhythmias did not occur and atrial refractoriness was unchanged. Thus, a minimal blood pressure response to hydralazine was associated with enhanced automaticity. Hydralazine merits clinical trial for treatment of sick sinus syndrome with concomitant hypertension.

The "R-on-T" phenomenon: an update and critical review.

The "R-on-T phenomenon" is the superimposition of an ectopic beat on the T wave of a preceding beat. Early observations suggested that R-on-T was likely to initiate sustained ventricular tachyarrhythmias. More recent experimental and clinical observations suggest that R-on-T is not a critical determinant of primary ventricular fibrillation in acute myocardial infarction; represents few of the initiating beats of paroxysmal ventricular tachycardia; and represents at worst only a small risk in terms of sudden death. Apparently when the capacity for sustained repetitive beating has not been clinically obvious, R-on-T is quite unlikely to result in ventricular tachyarrhythmias, even in the presence of coronary heart disease. However, in the setting of acute myocardial infarction, inability to always identify the precursors of tachyarrhythmias strengthens the argument for prophylactic treatment of patients.

Congenital coronary arteriovenous fistula: a diagnostic challenge.

This report describes a case of coronary arteriovenous (A-V) fistula involving both the right and the left coronary arteries. The venous component of the two circulations combines into a single channel that empties into the left ventricle just below the mitral valve.

Propranolol in mitral stenosis during sinus rhythm.

Patients with early symptomatic mitral stenosis usually suffer from pulmonary congestion on the basis of left atrial and pulmonary venous hypertension. They are often in sinus rhythm, and cardiac output is usually well maintained. Symptoms occur most often when heart rate, cardiac output, or both are increased. In this study, intravenous propranolol administered to patients with pure mitral stenosis in sinus rhythm resulted in significant reductions in mitral diastolic gradient (-7.1 mm. Hg +/- 1.6 SED), mean pulmonary wedge pressure (--6.9 mm. Hg +/- 1.2) and mean pulmonary artery pressures (--9.0 mm. Hg +/- 1.2). This was due to simultaneous reduction of heart rate (--13.0 beats/minute +/- 2.6 and cardiac output (--0.5 L./minute +/- 0.2). A small associated reduction of left ventricular systolic pressure (--5.1 mm. Hg +/- 2.6) was not accompanied by adverse clinical effects. A potential role for propranolol in medical management of pure mitral stenosis in the presence of sinus rhythm is suggested.