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Biomedical subjects

K Venkataraman

Publications and source records attributed to K Venkataraman.

At least 37 records · Page 2Linked to original sources
PubMed1986

Efficacy and safety of nicardipine for chronic, stable angina pectoris: a multicenter randomized trial.

Nicardipine, a new calcium channel blocking drug of the dihydropyridine family, was administered to 63 patients at a dose of 30 or 40 mg 3 times daily in a multicenter, randomized, double-blind, placebo-controlled, crossover trial. Nicardipine midly increased heart rate (HR) at rest and midly decreased the blood pressure (BP) at rest. When generally similar responses to the 30- and 40-mg doses were averaged, nicardipine produced a 7% increase in peak exercise HR, which was balanced by a 6% decrease in peak exercise BP. Thus, no change occurred in the exercise HR-BP product. With nicardipine, treadmill exercise duration increased 9%, time to angina increased 15%, time to 1-mm ST-segment depression increased 16%, and oxygen consumption at peak exercise increased 13%. Mean anginal frequency declined, as did mean weekly sublingual nitroglycerin consumption, but not significantly. There were more cardiovascular side effects with nicardipine than with placebo, with at least 3 patients having increased angina judged by investigators as probably related to the drug. Vasodilatory side effects were also more frequent with nicardipine, but were generally mild and well tolerated; the drug had to be discontinued in only 1 patient, because of vasodilatory effects. Nicardipine is effective and generally well tolerated in patients with chronic stable angina.

Adult↗
PubMed1986

Diltiazem as monotherapy for systemic hypertension: a multicenter, randomized, placebo-controlled trial.

A multicenter, randomized, placebo-controlled, parallel group study of diltiazem in essential hypertension was carried out in 77 patients (40 diltiazem, 37 placebo) with stable supine diastolic blood pressure (BP) between 95 and 110 mm Hg. Patients were withdrawn from previous antihypertensive therapy for at least 4 weeks, titrated to the optimal dose, and followed for a total of 12 weeks during therapy. A diltiazem dose of 360 mg/day was required in 85% of the patients. Average BP in all positions was significantly (p less than 0.0001) reduced by diltiazem compared with placebo. With diltiazem, average supine BP fell from 156/100 mm Hg at baseline to 141/87 at end titration and 145/90 mm Hg at week 12, whereas average standing BP fell from 152/101 mm Hg to 136/90 and 143/91 mm Hg, respectively, at those times. There was no significant change in heart rate at week 12. Diltiazem tended to be more effective in older patients, but caused no increase in orthostatic BP drop. There were no statistically significant changes in BP in the placebo group. Two patients receiving placebo and 1 patient receiving diltiazem discontinued therapy as a result of adverse effects, and overall, side effects were only slightly more common with diltiazem treatment. Thus, diltiazem was effective and well tolerated single therapy for mild to moderate systemic hypertension and appears to compare favorably to most agents being used.

Age Factors↗
PubMed1986

Knotting of a bypass graft catheter: report of a case.

A case of knotting of a bypass graft catheter during coronary arteriography is presented. An arteriotomy had to be done to remove the catheter. A possible mechanism causing this complication and precautions to avoid it are described.

Angiography↗
PubMed1985

Nicardipine for stable angina pectoris.

Nicardipine, 30 and 40 mg thrice daily, was administered to 66 patients with stable angina pectoris in a multicentre, randomised, double-blind, cross-over trial. With nicardipine therapy, duration of exercise and cumulative oxygen consumption increased, while times to onset of angina and 1 mm ST segment depression were prolonged. Anginal frequency and nitroglycerin consumption declined with use of nicardipine, but this did not reach statistical significance. Resting heart rate increased slightly and resting blood pressure decreased. Two patients on nicardipine and one on placebo sustained acute infarction. Otherwise, side effects were generally mild and transient.

Adult↗
PubMed1984

Longterm complications of Beall prosthetic valve: a case report.

A case of malfunctioning Beall prosthetic mitral valve causing severe heart failure is presented. The unusual aspect of this malfunction was the finding of disc dislodgment despite the absence of pathology in the disc itself. The dislodgment was caused by excessive tissue ingrowth around the suture ring. The need for close clinical follow-up of this type of prosthetic valve is emphasized.

Equipment Failure↗
PubMed1980

Fascicular premature beats with narrow QRS in the presence of bundle-branch block.

The electrocardiogram of a sixty-two-year-old male revealed right bundle-branch block, left anterior superior fascicular block, and right precordial Q waves consistent with anteroseptal myocardial infarction. Premature beats with narrow QRS (100 ms) occurred intermittently; coupling intervals varied between 560-600 ms. His bundle electrogram confirmed the fascicular origin of the premature beats. During atrial prematuring studies, it was shown that an appropriately timed premature beat could prolong infra-His conduction time, but QRS normalization was not achieved. The possible electrophysiologic mechanisms that could result in a normal QRS complex with fascicular premature beats in this patient are discussed; a new mechanism is suggested.

Arrhythmias, Cardiac↗
PubMed1980

Clinical experience with a programmable pacemaker.

As part of a study to evaluate a new programmable pacemaker, 15 patients received lithium-powered R-wave inhibited, unipolar pulse-generators (CPI Model 0505). Five were initial implants (Group I) and 10 were pulse generator replacements (Group II). The follow-up period ranged from 1 to 18 months (mean 11 months). There were 5 deaths unrelated to the pacemaker. Three instances of pacemaker failure were identified and were characterized by a sudden loss of pacemaker output. THe malfunction, traced to a 10 kHz timing crystal, has been corrected in subsequently manufactured pulse-generators. In 11 patients, the pacemakers were programmed at a pulse width which was twice the threshold determined at 3 months. Four were programmed at 0.1 ms, three at 0.2 ms and four at 0.4 ms. Although no complications were seen in patients programmed at 0.1 ms pulse width, it might be advisable to leave pacemakers at 0.2 ms or greater for chronic pacing in patients with a pulse width threshold at 0.05 mg.

Aged↗
PubMed1980

Thrombosis of Björk-Shiley aortic valve prostheses.

Though thromboembolic complications are reportedly minimal in patients with Björk-Shiley aortic valve prostheses, massive thrombosis remains a major and often fatal problem. The authors observed massive thrombosis in 3 patients, only one of whom survived. In all three instances, the disk of the prosthesis was relatively radiolucent. With valves manufactured after late 1975, which contain a tantalum foil hoop, cineradiography is the most rapid and accurate method of showing the disk. A simple method of calculating the valve opening angle from the cineradiograph is described. It is suggested that serial cineradiographs might be useful in detecting lesser degrees of thrombosis and partial immobilization of the disk.

Aortic Valve↗
PubMed1980

Reduction of myocardial ischemic injury with sublingual isosorbide dinitrate.

Twenty-one patients with acute anterior myocardial infarction had precordial ST segment mapping, using a system of 42 leads, at 0, 2, 4, 8, 24, and 48 hours (control group). Eleven patients (treatment group) had maps on admission and after 30-45 minutes; then serial maps were performed at similar intervals after 5-10 mg of isosorbide dinitrate (ISD). There were no significant differences in age, sex, functional class, mean time elapsed between onset of chest pain and admission, and inhospital mortality between the groups. Controls had a higher incidence of recurrent MI (6 patients vs 2) compared with the ISD group (P less than 0.05).The sum of ST segment elevations in all leads (ΣST) was similar in both groups on admission and remained at the same level in controls for 48 hours. One hour after ISD the blood pressure decreased significantly; ΣST and the number of leads with more than 1 mm ST elevation (NST) decreased significantly (62±10 to 31±4 / 26±1 to 19±2) (P less than 0.01). In the ISD group serial ST maps showed significant decreases (52±5 vs 28±4; 44±4 vs 26±2; 45±4 vs 29±3; 51±5 vs 28±3, 52±8 vs 28±2, respectively at 2, 4, 8, 24 and 48 hours), suggesting reduction of ischemic injury by ISD.Estimation of infarct size (in units from R wave height and Q and S wave depths in leads I, AVL and V(1)-V(6)) indicated a reduction in the ISD group on days one, two and seven. Total CPK, SGOT and LDH levels were similar on admission; at 24 and 48 hours after admission CPK values were not significantly different but SGOT and LDH were lower in the treated group.

Aged↗
PubMed1979

Isosorbide dinitrate in acute and chronic heart failure.

The hemodynamic effects of sublingual isosorbide dinitrate (ISD) were studied in 12 patients with congestive heart failure (CHF) of many causes. The duration of CHF in the chronic group varied from 3 to 62 months (mean, 29.5). Hemodynamic parameters were obtained serially before and 10, 20, 30, 45, 60, and 120 min after a 5 to 15 mg dose of ISD sublingually. The hemodynamic effects were pronounced at 45 min and returned to control levels in 120 min. Heart rate did not change. Hemodynamic parameters that changed after ISD were mean arterial pressure (-7%, p less than 0.05), mean pulmonary artery pressure (-17%, p less than 0.05), and mean pulmonary capillary wedge pressure (-29%, p less than 0.005). Mean cardiac index (+3%, p = NS) and mean stroke work index rose (+9.4%, P X NS); mean total systemic resistance fell (-10%, p = NS). Thus the duration of hemodynamic effects of ISD is less than 2 hr and sublingual ISD induces beneficial reduction of pulmonary capillary wedge pressure in patients with acute and chronic CHF without increasing cardiac index and stroke work index.

Acute Disease↗
PubMed1979

Intracardiac electrocardiography during permanent pacemaker implantation: predictors of cardiac perforation.

Intracardiac electrograms from 50 successive patients undergoing permanent pacemaker implantation have been analyzed. There were 29 male and 21 female patients aged 14 to 93 years (mean age 68.4 years). The electrograms were obtained using methods that simulated the wave form that would be detected by unipolar cardiac pacemakers. Three types of electrographic patterns were identified: qR pattern with a q/R ratio of less than 1 (type I): QR pattern with a Q/R ratio between 1 and 4.4 (type II); and Qr pattern with a Q/r ratio between 12 and 15 (type III). A type I pattern was seen in 29 patients (58 percent), type II in 18 (36 percent) and type III in 3 patients (6 percent). The duration of the follow-up period ranged from 3 weeks to 20 months (mean 9.7 months); three patients were lost to follow-up study. There were four deaths apparently unrelated to the pacemaker. Recognizable problems (either pacing or sensing failure) occurred in one patient (6 percent) with a type II pattern, in two patients (66.7 percent) with a type III pattern and in no patient with a type I pattern. On the basis of these data it is suggested that at the time of pacemaker implantation, intracardiac electrograms with a type I pattern indicating good pacing thresholds and sensing should be sought. If type II wave forms occur with good pacing thresholds and sensing then the electrode could probably be left in position. The incidence of a type III pattern is rare; when it does occur it is greatly suggestive of myocardial perforation. When this pattern is seen, the pacemaker catheter must be repositioned.

Adolescent↗
PubMed1979

Diastolic flutter of aortic valves in aortic regurgitation: a report of seven cases.

Seven patients with aortic regurgitation, manifesting diastolic flutter of the aortic valve cusps (DFAVC) in the echograms, are described. Five patients with infective endocarditis revealed coarse or fine, irregular DFAVC. Two patients with severe aortic regurgitation and a musical murmur manifested regular DFAVC with a frequency identical to that of a simultaneously recorded diastolic murmur. Of the 5 patients with infective endocarditis, 4 required urgent aortic valve replacement and 1 died. The 2 patients with musical murmurs are clinically stable without surgery. This report extends the clinical spectrum of patients with DFAVC and describes the character of the flutter in patients with muscial murmurs. Furthermore, it suggests that DFAVC is a sign of severe aortic regurgitation.

Adult↗
PubMed1979

Negative P waves in lead V6 during right ventricular pacing.

A negative P wave in lead V6 has been proposed as the most reliable criterion of left atrial rhythm, useful in differentiating it from nodal arrhythmias. In this report the electrocardiograms of two patients with right ventricular paced rhythms with 1:1 retrograde atrial capture are shown. The retrograde P waves inscribed after the ORS were negative in polarity in lead V6 in both cases. This documents that an impulse entering the atria from the AV junction can be associated with rightwardly oriented P waves and suggests that the proposed criterion for left atrial rhythm is unreliable.

Aged↗
PubMed1978

Musical murmurs: an echo-phonocardiographic study.

Five patients with muscial murmurs were studied noninvasively with simultaneous echocardiography and phonocardiograpy and phonocardiography. Three patients had aortic regurgitation, one mitral regurgitation and one tricuspid regurgitation. The frequency of the muscial murmurs ranged from 40 to 158 cycles/sec. The patient with tricuspid regurgitation manifested an inspiratory honk. Simultaneous echo-phonocardiography revealed regular valve leaflet flutter (aortic, mitral or tricuspid) at a frequency identical to that of the simultaneously recorded muscial murmur. This study demonstrates that echocardiography is a useful noninvasive tool in identifying the site of origin of musical murmurs.

Adult↗
PubMed1978

Problems in ultrasonic estimates of septal thickness.

Problems related to cardiac anatomy and ultrasonic instrumentation affect the accuracy of echographic identification of endocardial echoes. A cadaver model and 13 patients were studied, with direct identification or with the aid of echographic contrast techniques, to identify accurately the endocardial echo. The study showed that (1) echographic contrast agents delineate an endocardial echo in the central portion of the ultransonic beam; (2) a specular reflector exists within the right ventricular cavity; (3) specular reflectors within the septum may give the false appearance of border-forming echoes; (4) septal thickness varies by 1 to 5 mm after the endocardial echo has been identified by the contrast agent; and (5) spurious echoes, related to a wide beam angle, can be confused with the endocardial echo. In light of these problems, three criteria were utilized for endocardial echo identification: the prominent notch in the left septal echo, the specular quality of the right septal echo, and the association of multiple myocardial echoes moving in parallel. With these criteria, the endocardial echoes in 11 of the 13 patients could be accurately identified without the use of a contrast agent. The identification of these problems should provide helpful guidelines in developing more accurate and reproducible criteria for septal thickness measurements.

Cadaver↗