Richard B. Whiting

Sensitivity and specificity of commonly used electrocardiographic criteria for left atrial enlargement determined by m-mode echocardiography

To assess the sensitivity and specificity of 6 commonly used electrocardiographic criteria for left atrial (LA) enlargement, the rest ECGs of 99 patients in normal sinus rhythm were analyzed. Fifty-seven of the patients had LA enlargement and 42 had a normal LA dimension as determined by M-mode echocardiography. The 6 criteria studied and their respective sensitivities and specificities were as follows: (1) duration of the negative phase of the P wave in lead V1 greater than 40 ms: sensitivity, 83%; specificity, 80%; (2) notched P wave in any standard lead with an interpeak duration greater than 40 ms: sensitivity, 15%; specificity, 100%; (3) P terminal force (depth X duration of the terminal portion of the P wave) in lead V1 more negative than -0.04 mm X s: sensitivity, 69%; specificity 93%; (4) depth of the negative phase of the P wave in lead V1 greater than or equal to 1 mm: sensitivity, 60%; specificity, 93%; (5) total P-wave duration greater than 110 ms in any standard lead: sensitivity, 33%; specificity, 88%; (6) total P wave duration/P-R interval duration greater than 1.6: sensitivity, 31%; specificity, 64%. Combining 2 or more of these criteria did not substantially improve sensitivity and specificity.

Effect of hemodialysis on left ventricular performance. Analysis of echocardiographic subsets

To assess the effect of hemodialysis on left ventricular performance, we performed M-mode echocardiography on 31 patients with end-stage renal disease prior to and immediately following 4-hour chronic maintenance hemodialysis. Overall, hemodialysis produced a significant increase in mean heart rate and the mean velocity of circumferential fiber shortening (mean Vcf), a significant decrease in mean stroke index and no significant change in mean cardiac index. Hemodialysis resulted in a significant increase in mean Vcf in the subset of patients with reduced mean Vcf prior to dialysis, but produced no significant change in mean Vcf in the group with normal predialysis mean Vcf. Hemodialysis resulted in a significant increase in mean Vcf in the subset of patients with normal left ventricular end-diastolic volume prior to dialysis, but produced no significant change in mean Vcf in the group with increased predialysis left ventricular end-diastolic volume. The presence of left ventricular hypertrophy appeared to blunt the expected increase in mean Vcf in the group with reduced mean Vcf prior to hemodialysis. These results suggest that predialysis left ventricular volume, wall thickness and contractility are important determinants of the effect of hemodialysis on left ventricular performance.

Sensitivity and specificity of M mode echocardiographic signs of mitral valve prolapse

To assess the sensitivity and specificity of previously described M mode echocardiographic signs of mitral valve prolapse, 100 subjects with a mobile mid systolic click and 100 matched normal control subjects were prospectively studied. Late systolic posterior motion and holosystolic hammocking of the mitral leaflets were common, highly specific signs of mitral valve prolapse. When these signs were combined as a single criterion, sensitivity was 85 percent and specificity was 99 percent. Other signs, including systolic echoes in the mid left atrium, systolic anterior motion, early diastolic anterior motion of the posterior mitral leaflet and shaggy or heavy cascading linear diastolic echoes posterior to the mitral valve, were highly specific but uncommon. They occurred only in combination with late systolic posterior motion or holosystolic hammocking. The remaining signs tested did not differentiate subjects with mitral valve prolapse from normal persons.

Clinical Experience with Permanent Atrioventricular Sequential Pacing

In a 23-moth period, we implanted 26 permanent atrioventricular (AV) sequential pacing units in 11 women and 15 men ranging from 37 to 85 years old (mean, 68 years). Indications for pacing were complete heart block n 12 patients and sick sinus syndrome in 14 patients. Cardiac index, using standard thermodilution techniques, was determined in 9 patients during ventricular pacing and AV sequential pacing at constant heart rate. Atrioventricular sequential pacing was superior in all patients, with a mean increase in cardiac index of 22% (p greater than 0.01). Complications of AV sequential pacing included the need to revise two pulse generator pockets due to the large size of the pulse generator. One transvenous atrial lead displacement occurred in a patient who had previously undergone right atrial appendage ligation at open-heart operation. No failures of pacing or sensing occurred during 279 patient-paced months. The theoretical hemodynamic advantage of AV sequential pacing has been confirmed in this clinical trial. Experience with electrode placement and improvements in pulse generator design should aid in eliminating complications with this pacing modality.

Symptomatic prognosis in patients with idiopathic hypertrophic subaortic stenosis (IHSS)

Abstract Twenty-nine patients with idiopathic hypertrophic subaortic stenosis (IHSS) catheterized in our institution during a three year period were studied prospectively to determine their prognosis following orally administered propranolol and to correlate this with the response to intravenously administered propranolol at catheterization. The median time to follow-up was 16 months. Before catheterization 5 patients had New York Heart Association class I heart disease, 14 class II, 7 class III and 3 class IV. Only 5 of 27 patients who received long-term propranolol therapy demonstrated symptomatic deterioration compared with 22 of 27 who showed no deterioration (p Division of the patients into three categories, i.e., those with latent, labile and persistent (> 30 mm Hg) left ventricular outflow tract gradients at the time of cardiac catheterization, did not provide a correlation with their prognosis following oral propranolol therapy. Two patients died suddenly, both with minimal resting gradients. The abolition of a resting gradient, the reduction of the increase in gradient associated with a Valsalva maneuver or with the administration of nitroglycerin, all by the acute administration of intravenous propranolol, also was of no prognostic value. This study indicates that in most patients with IHSS symptoms diminish or stabilize during therapy with oral propranolol. The data further emphasize that sudden death in IHSS (presumably arrhythmic) occurs in the presence of minimal outflow tract obstruction. This study stresses the difficulty in predicting in which patients with IHSS symptoms will stabilize or diminish on long-term oral propranolol therapy.

Wheelchair exercise testing: comparison of continuous and discontinuous exercise

We have compared wheelchair exercise performed at submaximal levels in a continuous versus discontinuous format. There was a positive linear relationship between heart rate, systolic blood pressure, and VO2 with increasing workload. This was true for both modes of testing with no significant difference in heart rate, systolic blood pressure, VO2, Ve, or Ve/VO2. We conclude that clinical wheelchair exercise testing can be performed in a continuous format without sacrificing physiological data.

Atrioventricular sequential pacing: comparison with ventricular pacing using systolic time intervals.

Nine patients with programmable atrioventricular sequential pacers were studied using systolic time intervals (QS2—the total electrical and mechanical systole, left ventricular ejection time, and pre‐ejeclion period). These measurements were obtained by simultaneous recording of the electrocardiogram, phonocardiogram. and carotid pulse tracing. There was a dramatic fall of left ventricular ejection time (LVET) and an increase of the pre‐ejection time (PEP) in all patients when the pacers were programmed from the atrioventricular to the ventricular mode at constant heart rate. This resulted in an increase of the ratio PEP/LVET from 428 to 574 suggesting loss of ventricular function. These measurements all reversed to baseline values when the pacers were reprogrammed back to the atrioventricular mode. This study suggests systolic time intervals might be useful to select non‐invasively pacer parameters such as mode, rate, and effective PR interval in order to provide the best hemodynamics in a given patient.

Lactic dehydrogenase and fraction 1 in acute myocardial infarction.

Serum enzyme determinations have been a regular part of the clinical evaluation of patients with possible acute myocardial infarction for many years. Several conditions, however, may mimic acute infarction, and there has been a desire for more specific enzyme determinations. The diagnostic value of lactic dehydrogenase (LDH) has been considerably enhanced by electrophoretic separation into its 5 isozyme fractions, which are distributed