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Biomedical subjects

S H Rahimtoola

Publications and source records attributed to S H Rahimtoola.

At least 73 records · Page 4Linked to original sources
PubMed1991

Randomized study to evaluate the relation between oral isosorbide dinitrate dosing interval and the development of early tolerance to its effect on left ventricular filling pressure in patients with chronic heart failure.

BACKGROUND: Early development of nitrate tolerance has been shown in patients with chronic congestive heart failure (CHF) receiving continuous nitroglycerin therapy. The influence of dosing interval of oral isosorbide dinitrate (ISDN), the nitrate preparation most widely used for the treatment of CHF, has not been investigated. METHODS AND RESULTS: We performed a prospective, randomized study to evaluate the effect of various regimens of oral ISDN on the development of early tolerance to its effect on left ventricular filling pressure in patients with moderate to severe CHF. Forty-four responders (20% or greater reduction in mean pulmonary artery wedge pressure lasting 1 hour or longer) were divided into four groups of 11 patients each, and randomized to receive their effective ISDN dose (40-120 mg) Q 4 hours, Q 6 hours, Q 8 hours, or t.i.d. (drug given at 0, 6, 12, and 24 hours allowing 12 hours of ISDN washout interval between the third and fourth doses). All groups demonstrated a significant and comparable reduction in LV filling pressure following administration of the first ISDN dose. Early attenuation of hemodynamic response was demonstrated with frequent dosing (Q 4 hours and Q 6 hours) ISDN. Tolerance was with a Q 8-hour regimen as demonstrated by preserved hemodynamic response to each dose. The effect of each dose, however, was short-term, with return of pulmonary artery wedge pressure to baseline level at 2 to 4 hours, resulting in an intermittent effect totaling no longer than 12 hours of the 30-hour study period. The use of a t.i.d. regimen resulted in marked attenuation of response after the third dose with complete restoration of nitrate effect following a 12-hour washout period between the third and fourth doses. ISDN plasma concentration was measured in five patients in each of the Q 4- and Q 8-hour groups. In the Q 4-hour group, plasma levels were significantly higher after administration of the last dose than after the first dose (area under the curve, 242 +/- 216 versus 123 +/- 130 ng/ml, p less than 0.05), and trough levels before administration of the second and the fifth dose (15 +/- 17 and 27 +/- 27 ng/ml, respectively) were both markedly higher than the baseline value of 2 +/- 4 ng/ml. CONCLUSIONS: Our data demonstrate the development of tolerance and early attenuation of effect on left ventricular filling pressure with frequent oral dosing (Q 4 and Q 6 hours) with ISDN in patients with chronic CHF, which may be related to persistently elevated trough blood levels of ISDN. The development of tolerance can be reversed after a washout period of 12 hours and can be prevented with a Q 8-hour administration. These regimens, however, are limited by an inconsistent effect. Although long-term implications of these findings need further evaluation, the present study demonstrates the difficulty of maintaining a persistent ISDN-mediated reduction in left ventricular filling pressure in patients with chronic, moderate to severe CHF. These results suggest the need to use intermittent ISDN therapy allowing a daily nitrate washout interval and the rationale for combined vasodilator therapy in patients with CHF.

Drug Administration Schedule↗
PubMed1991

The role of echocardiography/Doppler in catheter balloon treatment of adults with aortic and mitral stenosis.

Doppler and two-dimensional echocardiography (2DE) have played a major role in the evaluation of patients undergoing catheter balloon treatment of aortic and mitral stenosis. Doppler/2DE has made possible an understanding of the mechanism of increase in valve area. Before the procedure, Doppler/2DE provides a reasonable estimate of the severity of the valvular stenosis and associated cardiac abnormalities. The evaluation of mitral valve morphology by 2DE before catheter balloon treatment has shown that patients with excellent leaflet motion and minimal increase in valve thickness have the greatest increase in mitral valve area. During the procedure, Doppler/2DE can aid in the transseptal puncture, in positioning the balloons across the stenotic orifice, and in the immediate assessment of changes in valve function and complications. The estimate of the aortic and mitral valve gradients and areas by Doppler/2DE before catheter balloon treatment shows a reasonable correlation with hemodynamic measurements. Immediately after the procedure, the Doppler/2DE estimates of aortic valve gradient and area show a fair correlation with data from cardiac catheterization, provided care is taken to avoid technical problems. Doppler/2DE assessment of mitral valve area immediately after catheter balloon commissurotomy (CBC) shows a poor correlation with catheterization data, which has been attributed to rapid changes in left atrial compliance and gradient. However, the correlation of Doppler estimates of mitral valve area with catheterization data improves at 3 months after CBC. Serial evaluations of patients after aortic or mitral catheter balloon dilatation should permit detection of restenosis and valve regurgitation and assessment of ventricular function and may provide valuable insights into the mechanisms of restenosis and changing clinical status.

Adult↗
PubMed1991

Clinical overview of management of chronic ischemic heart disease.

The outcome of patients with chronic coronary artery disease is dependent on many factors; the most important ones include the severity and extent of coronary artery disease, state of left ventricular function at rest, extent and severity of myocardial ischemia, and the total amount of left ventricular myocardium that is at risk. To use noninvasive tests optimally, the clinician first must define the information needed. The sensitivity, specificity, and predictive accuracy of the test(s) in providing the necessary information, the additive value of the result of a test to the information already available, and the best combination of tests in providing the desired information help determine the choice of various noninvasive tests in a particular clinical circumstance.

Angioplasty, Balloon, Coronary↗
PubMed1990

The long-term prognosis of patients with out-of-hospital cardiac arrest but no inducible ventricular tachycardia.

The long-term prognosis of patients successfully resuscitated from cardiac arrest who do not have acute precipitating factors and in whom ventricular arrhythmias cannot be induced during baseline electrophysiologic testing is controversial. The purpose of this investigation was to evaluate the long-term risk of recurrent sudden death and determine the clinical, angiographic, hemodynamic, and electrophysiologic predictors of recurrent cardiac arrest in such patients. Twenty-six (37%) of 71 consecutive patients with a single episode of aborted sudden death did not have inducible ventricular arrhythmias (less than 7 intraventricular responses) during baseline drug-free electrophysiologic study and they form the basis of this report. Their mean age was 54 +/- 13 (mean +/- SD) years and the left ventricular ejection fraction (LVEF) was 0.47 +/- 0.17. After a mean follow-up period of 16 months, 11 patients (42%) had a recurrent cardiac arrest (fatal in 10 patients). The actuarial incidence of recurrent cardiac arrest was 30 +/- 10% at 1 year and 55 +/- 13% at 3 years. Patients with LVEF less than or equal to 0.40 had a significantly higher occurrence of recurrent cardiac arrest than those with LVEF greater than 0.40 (p = 0.02; 1-year actuarial incidence of 57 +/- 17% versus 13 +/- 19%). Patients with recurrent sudden death had a significantly greater incidence of dilated cardiomyopathy (55% versus 7%; p = 0.02) and baseline frequent premature ventricular contractions (PVCs greater than 10/hr; 64% versus 17%, p = 0.036) or nonsustained ventricular tachycardia (36% versus 0%; p = 0.37) than patients without these characteristics.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Day to day reproducibility of electrically inducible ventricular arrhythmias in survivors of acute myocardial infarction.

Day to day reproducibility of the response to programmed ventricular stimulation has not been evaluated in survivors of acute myocardial infarction. Programmed ventricular stimulation was performed prospectively on 2 consecutive days in 56 patients on an average of 12 +/- 5 days (range 7 to 29) after an acute myocardial infarction. No patient had a history of documented or suspected sustained ventricular tachycardia or fibrillation occurring greater than 48 h after infarction. During initial programmed ventricular stimulation, 21 patients had induction of sustained ventricular tachycardia or fibrillation (Group I), and 35 patients had induction of either nonsustained ventricular tachycardia or no ventricular tachycardia (Group II). Repeat programmed ventricular stimulation in Group I patients induced sustained ventricular tachycardia or fibrillation in 16 of 21 patients (reproducibility 76%); the maximal induced response in the other 5 patients was nonsustained ventricular tachycardia in 2 patients and fewer than six repetitive ventricular responses in 3 patients. The day to day reproducibility was significantly higher for inducible sustained ventricular tachycardia of cycle length greater than or equal to 240 ms compared with rapid sustained ventricular tachycardia of cycle length less than 240 ms (100% versus 44%, p less than 0.009) or ventricular fibrillation (100% versus 43%, p less than 0.009). Repeat programmed ventricular stimulation in Group II patients did not induce sustained ventricular arrhythmias in 31 of 35 patients (reproducibility 89%). Thus, in survivors of acute myocardial infarction, inducible slow sustained ventricular tachycardia was a highly reproducible finding, whereas inducibility of rapid sustained ventricular tachycardia and ventricular fibrillation showed a significant day to day variability.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Prospective evaluation of parenteral magnesium sulfate in the treatment of patients with reentrant AV supraventricular tachycardia.

This study prospectively assessed the electrophysiologic effects of parenteral magnesium sulfate administration on paroxysmal atrioventricular (AV) reentrant supraventricular tachycardia and the efficacy of magnesium to terminate these arrhythmias. Eleven normomagnesemic patients, seven with orthodromic reentrant supraventricular tachycardia that used an accessory AV pathway, and four with typical AV nodal reentry were examined. All patients had a history of sustained supraventricular tachycardia requiring pharmacologic therapy or electrical cardioversion for termination of tachycardia. After baseline electrophysiologic study, including documentation of sustained supraventricular tachycardia that was reproducibly induced, parenteral magnesium sulfate (a bolus of 0.3 mEq/kg of elemental magnesium infused over a 10-minute period followed by a maintenance infusion of 0.2 mEq/kg/hr) was administered during sustained supraventricular tachycardia. The serum magnesium concentration increased from (mean +/- standard deviation) 1.9 +/- 0.2 mg/dl to 4.0 +/- 0.6 mg/dl (p = 0.0001). Except for flushing and mild diaphoresis during infusion of the magnesium sulfate bolus, and dry heaves in one patient, there were no untoward effects or significant changes in systolic blood pressure. During administration of magnesium, the tachycardia cycle length increased from 319 +/- 39 msec to 348 +/- 43 msec (p = 0.0001). Slowing of the tachycardia occurred predominantly in the antegrade limb of the circuit at the level of the AV node with the AH interval increasing from 171 +/- 66 msec to 197 +/- 68 msec (p = 0.0001), whereas there was no significant change in the HV interval (43 +/- 3 msec to 43 +/- 4 msec, p = NS) or the VA interval (106 +/- 43 msec to 110 +/- 47 msec, p = NS) during tachycardia.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Significance of laminar systolic regurgitant flow in patients with tricuspid regurgitation: a combined pulsed-wave, continuous-wave Doppler and two-dimensional echocardiographic study.

To define the significance of laminar systolic tricuspid regurgitant (TR) flow, pulsed-wave and continuous-wave Doppler (PWD, CWD), and two-dimensional and M-mode echocardiography (2-DE, M-mode) were performed in 68 patients with TR, which included five patients with tricuspid valvectomy. The pattern of TR flow (laminar versus turbulent), TR severity (the distance that the regurgitant flow extended into the right atrium [1+ to 4+ as measured by PWD]), the peak flow velocity of TR by CWD, the presence or absence and the amount of systolic tricuspid cusp separation by 2-DE, and the dimension of the right ventricle and the inferior vena cava by M-mode, were assessed. A laminar pattern of TR flow in systole was obtained in 21 patients, five of whom had undergone tricuspid valvectomy. Fourteen of 21 had visible tricuspid cusp separation in systole on 2-DE; of the seven who had no visible tricuspid cusp separation during systole, five had undergone tricuspid valvectomy. All 47 patients with a turbulent pattern of TR flow had no visible systolic tricuspid cusp separation. Severe 4+ TR was present in 14 of 21 (67%) patients with laminar TR flow and in 4 of 47 (9%) patients with turbulent TR flow (p less than 0.001). The peak flow velocity of TR in patients with laminar TR flow (2.0 +/- 0.7 m/sec) was lower (p less than 0.001) than in those with turbulent TR flow (3.1 +/- 0.7 m/sec).(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗
PubMed1990

Effect of acute hemodynamic decompensation on electrical inducibility of ventricular arrhythmias in patients with dilated cardiomyopathy and complex nonsustained ventricular arrhythmias.

In patients with dilated cardiomyopathy, hemodynamic decompensation has been postulated to increase vulnerability to reentrant ventricular arrhythmias. To test this hypothesis, we performed programmed ventricular stimulation with three extrastimuli on nine patients with dilated cardiomyopathy and asymptomatic complex ventricular arrhythmias during a period of acute hemodynamic decompensation; programmed ventricular stimulation was then repeated following hemodynamic improvement with nitroprusside. These patients did not have a history of documented or suspected sustained ventricular tachycardia or fibrillation. The mean left ventricular ejection fraction was 0.21 +/- 0.04 (range 0.15 to 0.26). In the baseline state, mean right atrial pressure was 8 +/- 4 mm Hg, pulmonary artery wedge pressure was 20 +/- 3 mm Hg, and cardiac index was 3.2 +/- 0.5 L/min/m2. Following acute hemodynamic decompensation, mean right atrial pressure increased to 16 +/- 5 mm Hg and pulmonary artery wedge pressure to 33 +/- 8 mm Hg; cardiac index decreased to 2.1 +/- 0.5 L/min/m2. In this decompensated state, programmed ventricular stimulation failed to induce sustained or nonsustained ventricular arrhythmias in any patient. Following nitroprusside administration (mean dose 1.5 +/- 1.1 micrograms/kg/min), there were significant decreases in mean right atrial pressure (11 +/- 3 mm Hg) and pulmonary artery wedge pressure (16 +/- 3 mm Hg), and a significant increase in cardiac index (3.1 +/- 1.1 L/min/m2) (p less than 0.05 for all values versus the decompensated state). In the improved hemodynamic state, programmed ventricular stimulation induced nonsustained ventricular tachycardia (six beats) in only one patient, and sustained arrhythmias in none.(ABSTRACT TRUNCATED AT 250 WORDS)

Arrhythmias, Cardiac↗
PubMed1990

Accuracy of Doppler ultrasound in evaluating changes of left ventricular diastolic properties.

In order to evaluate the effect of an increase in preload caused by contrast medium (Renografin-75) on Doppler echocardiographic indices of left ventricular diastolic properties, left ventricular pressure using a catheter tip micromanometer and pulsed-Doppler measurement of transmitral flow signals were measured simultaneously in 15 patients with coronary artery disease pre- and post-left ventricular angiography. After left ventricular angiography, changes in indices determined from left ventricular pressure were significant: left ventricular end-diastolic pressure increased from 17 +/- 2 mmHg to 24 +/- 2 mmHg (mean +/- SE) (P less than 0.001), maximum -dP/dt increased from 1,129 +/- 63 to 1,307 +/- 90 mmHg/sec (P less than 0.005), and time constant decreased from 73 +/- 2 to 67 +/- 1 msec (P less than 0.01). Changes in Doppler-derived indices were also significant: A/E ratio decreased from 0.99 +/- 0.08 to 0.81 +/- 0.07 (P less than 0.01), peak velocity of early diastolic filling increased from 0.61 +/- 0.03 to 0.79 +/- 0.03 M/sec (P less than 0.01), and deceleration rate increased from 3.1 +/- 0.2 to 4.6 +/- 0.2 M/sec 2 (P less than 0.01). Changes in Doppler echocardiographic indices (DR, acceleration half time, deceleration half time, and A/E ratio) were accompanied by changes in time constant and maximum -dP/dt after left ventricular angiography. However, the correlations between changes in hemodynamic indices and changes in Doppler echocardiographic indices were poor (r = 0.06 to 0.67).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Artificial heart valves.

This overview of heart valve prostheses is based on a current review of clinical reports and focuses on the major complications that characterize long-term valve performance: thromboembolism, thrombosis, anti-coagulant-related bleeding, and structural failure.

Bioprosthesis↗