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Biomedical subjects

R B Whiting

Publications and source records attributed to R B Whiting.

At least 19 recordsLinked to original sources
PubMed1986

Comparative cardiac effects of hemodialysis and continuous ambulatory peritoneal dialysis.

To assess the comparative cardiac effects of hemodialysis and continuous ambulatory peritoneal dialysis (CAPD), we performed M-mode echocardiography prior to and immediately following hemodialysis on 56 patients and during the dwell phase of CAPD on 39 patients. Hemodialysis produced a significant increase in the mean velocity of circumferential fiber shortening (VCF, an index of left ventricular systolic function) in patients with low VCF prior to dialysis, but resulted in no significant change in VCF in patients with normal predialysis VCF. Hemodialysis produced a significant increase in VCF in patients with a normal predialysis left ventricular end-diastolic volume index (LVEDVI), but resulted in no significant change in VCF in patients with left ventricular dilatation prior to dialysis. Hemodialysis produced a significant decrease in mean LVEDVI and mean stroke index, but resulted in no significant change in mean cardiac index due to a reflex increase in heart rate. Mean LVEDVI, mean stroke index, and VCF values in patients on CAPD were not significantly different from those observed immediately following hemodialysis. Mean cardiac index and mean heart rate were significantly lower in CAPD patients than in posthemodialysis patients. Pericardial effusion was observed in 25% of hemodialysis patients and 5% of CAPD patients (p less than 0.05). We conclude (1) the effects of hemodialysis on left ventricular performance are variable and depend in part on predialysis left ventricular volume and left ventricular systolic function, (2) except for a lower cardiac index, left ventricular hemodynamics for CAPD patients resemble those of posthemodialysis patients, and (3) pericardial effusion occurs with significantly higher frequency in patients on hemodialysis than in those on CAPD.

Cardiac Output↗
PubMed1984

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.

Cardiomegaly↗
PubMed1984

Thromboembolism in patients with atrial fibrillation.

On retrospective review of records of 150 patients with atrial fibrillation (AF), 31% experienced a stroke or peripheral embolism. The AF was not associated with cardiac valvular disease in 80% of the 150 patients. Most of the cerebral infarcts were large, disabling, and unheralded by transient ischemic attack. The thromboembolism typically occurred in patients whose AF was undetected prior to the infarction. Half of the patients with an ischemic event suffered multiple events, with one fourth of the recurrences arising within two weeks.

Adult↗
PubMed1984

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.

Adult↗
PubMed1984

Symptomatic cardiac amyloidosis in an American family.

This report describes an American family with a high incidence of symptomatic cardiac amyloidosis among four siblings, and explores the role of echocardiography and technetium pyrophosphate myocardial scintigraphy in the detection of this infiltrative cardiomyopathy within the involved family.

Amyloidosis↗
PubMed1983

Clinical value of exercise testing in handicapped subjects.

This report describes the use of exercise testing in handicapped subjects to determine work capacity and the safety of exercise. Arm crank, bicycle, and wheelchair exercise studies are described by means of a few selected cases.

Adolescent↗
PubMed1983

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-ejection 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 re-programmed 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.

Aged↗
PubMed1982

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.

Adult↗
PubMed1982

Increased left ventricular mass in idiopathic mitral valve prolapse.

We performed M-mode echocardiography on 100 subjects with idiopathic mitral valve prolapse (IMVP) and on 100 normal control subjects to determine if differences exist between the two groups in cardiac chamber size, left ventricular performance or left ventricular mass. Subjects with IMVP demonstrated significantly greater left ventricular mass than normal control subjects. There were no significant differences in fractional shortening of the left ventricle or left ventricular end-diastolic volume. There was no significant difference in left ventricular mass between asymptomatic subjects with IMVP and those with chest pain, palpitations, syncope or presyncope. Subjects with and without mitral regurgitation showed no significant difference in mass. The results indicate that subjects with IMVP demonstrate subtle left ventricular hypertrophy which does not appear to be caused by underlying organic heart disease, mitral regurgitation or sustained hypercontractility. This suggests that myocardial involvement is an integral part of the IMVP syndrome.

Adult↗
PubMed1981

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.

Adult↗
PubMed1980

Toxic synergism of disopyramide and hyperkalemia.

A patient is presented whose electrocardiogram became remarkably abnormal and who developed hypotension while receiving disopyramide and potassium. This report documents a potassium-disopyramide synergism leading to life-threatening toxicity. These abnormalities were corrected by glucose, insulin and bicarbonate therapy, suggesting that serious disopyramide toxicity may be enhanced by hyperkalemia and reversed by lowering the serum potassium.

Aged↗
PubMed1980

Ventricular premature contractions. Which should be treated?

The treatment of ventricular premature contractions (VPCs) is based on two factors: bothersome symptoms from which the patient desires relief and the association of ectopic ventricular beats with sudden cardiac death. The sudden death risk related to ventricular ectopic beats is real, but appears to be a function of the frequency or pattern in which they occur plus the presence of underlying heart disease. A serious risk exists when frequent, multifocal, successive, or R-on-T-type VPCs occur in a patient monitored late after a fresh myocardial infarction, particularly if left ventricular failure is also present. Current data have been used to formulate levels of risk for sudden cardiac death on the basis of ventricular ectopic beats, which in turn provides a reasonable basis for the treatment of asymptomatic ventricular ectopy.

Adult↗