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Biomedical subjects

V Bala Subramanian

Publications and source records attributed to V Bala Subramanian.

14 recordsLinked to original sources
PubMed1998

Reference typing report for complement receptor 1 (CR1).

A total of 100 Chinese blood donors (50 from Shen-Zhen and 50 from Taiwan) were studied by the participants in addition to 9 reference samples. A new nomenclature for the CR1 structural alleles was recommended by the participants which would use a numbering system, e.g. CR1*1. The structural allele frequencies in the Chinese were: CR1*1 (190 kD) 0.96, CR1*2 (220 kD) 0.03, CR1*3 (160 kD) 0.01 and CR1*4 (250 kD) 0.00. The HindIII expression polymorphism was also studied and the high expressing allele had a gene frequency of 0.71 while the low expressor gene frequency was 0.28. Erythrocyte copy numbers were quantified and compared between laboratories with good correlation (R = 0.55-0.88). The mean (+/- SD) erythrocyte copy number was 463 (+/- 229) in the Taiwan donors and 446 (+/- 207) in the Mainland Chinese.

Alleles↗
PubMed1986

Clinical and research applications of ambulatory Holter ST-segment and heart rate monitoring.

Monitoring of the electrocardiogram during normal daily activity yields data regarding silent myocardial ischemia and its relation to heart rate in addition to the detection of cardiac arrhythmias. In recent years various techniques have been developed to quantify the frequency and duration of ischemic episodes in patients with ischemic heart disease. Of particular importance are the newer frequency-modulated recording techniques, which ensure adequate low frequency response, and the computerized digital analysis used to define the role of ST-segment monitoring in the clinical and research setting. The techniques used for acquiring artifact-free signals, the methods of data analysis and the clinical role of ambulatory Holter monitoring of ST-segment changes in the diagnosis of Prinzmetal's angina, in chronic stable angina and in the detection of calcium antagonist withdrawal syndrome in angina are discussed. The data indicate the particular utility of Holter monitoring to analyze the variability of heart rate in defining the effects of calcium-channel blockers, beta-adrenergic blocking agents and their combined use in pharmacologic therapy of ischemic myocardial syndromes.

Adrenergic beta-Antagonists↗
PubMed1984

Long-term efficacy of diltiazem assessed with multistage graded exercise tests in patients with chronic stable angina pectoris.

The long-term efficacy of diltiazem, 360 mg/day, in patients with grade II or III stable exertional angina pectoris (Canadian Cardiovascular Society criteria) was assessed by multistage graded exercise tests. Seventeen patients undertook a placebo-controlled, double-blind, dose-titration protocol and all received long-term therapy. Exercise tests were performed at the end of 2 weeks of placebo treatment and after 6, 18, 26, 40 and 52 weeks of diltiazem, 360 mg/day. All patients had angina during treadmill testing with placebo and the mean (+/- standard error of the mean) exercise time was 5.8 +/- 0.7 minutes. This increased to 10.8 +/- 1.0 minutes after 6 weeks, 11.3 +/- 1.1 minutes after 18 weeks, 11.4 +/- 1.1 minutes after 26 weeks, 12.9 +/- 1.2 minutes after 40 weeks and 11.6 +/- 1.3 minutes after 52 weeks of continuous diltiazem therapy (p less than 0.001 vs placebo at all stages). Four patients were withdrawn after 26 weeks of treatment; one patient underwent coronary artery bypass surgery and 3 patients required the addition of beta-adrenoreceptor blocking agents. In 1 patient an irritant rash developed on the torso, legs and arms after 39 weeks of diltiazem and disappeared after discontinuing the drug. One patient complained of swelling and stiffness of the fingers and 3 patients complained of shoulder and elbow pain. Another patient had a myocardial infarction after 8 weeks of diltiazem treatment and died. No other adverse effects were observed during this study.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1984

Efficacy of once daily penbutolol in chronic stable angina. An objective comparison with long-acting propranolol.

The effects of penbutolol (40 mg daily) and long-acting propranolol (160 mg daily) were assessed in 26 patients with chronic stable angina in a placebo-controlled randomised double-blind crossover study with 2-weekly treatment periods. In addition to conventional subjective assessment, serial multistage treadmill exercise was used to obtain objective data on drug efficacy and 24-hr ambulatory electrocardiography performed for diurnal heart rate analysis. The mean exercise time of 6.3 +/- 0.5 (SEM) min on placebo increased to 7.3 +/- 0.6 min on penbutolol (P less than 0.01) and to 7.9 +/- 0.5 min on propranolol (P less than 0.001). The pre-exercise resting heart rate was 73 +/- 2 beats/min on placebo and decreased to 63 +/- 2 beats/min on penbutolol (P less than 0.001) and 58 +/- 2 beats/min on propranolol (P less than 0.001). The maximum exercise heart rate was similarly reduced by both drugs and there was a corresponding reduction in peak exercise double product. The time-corrected maximum ST segment depression was reduced by both drugs and neither produced a delay in ST segment recovery. Both drugs effected significant reductions in ambulatory maximum hourly heart rates throughout 24 hr. The lowest observed heart rate on penbutolol was 40 beats/min and 34 beats/min on propranolol. Penbutolol is an effective antianginal agent with a profile of action similar to that of propranolol.

Aged↗
PubMed1984

Short- and long-term efficacy of nicardipine, assessed by placebo-controlled single- and double-blind crossover trials in patients with chronic stable angina.

The efficacy of nicardipine, a new calcium ion antagonist, was studied in 39 patients aged 42 to 70 years with chronic stable angina in two different placebo-controlled single- and double-blind crossover trials and with long-term follow-up, using serial quantitated exercise testing and ambulatory ST segment monitoring. In the first study the minimal effective dose was determined, and in the repeat study the effects of three different dose levels were evaluated. Treadmill exercise testing was performed at the end of each 2 week treatment period with on-line computer analysis of the electrocardiogram. The mean (+/- standard error of the mean) exercise time was 6.8 +/- 0.7 minutes on placebo and 7.0 +/- 0.8 minutes during treatment with nicardipine, 60 mg/day (p = NS). This increased to 8.7 +/- 0.8 (p less than 0.001) and 9.2 +/- 0.9 minutes (p less than 0.001) with 90 and 120 mg/day, respectively. The mean heart rate at rest during placebo administration was 75 +/- 2 beats/min and increased to 85 +/- 3, 84 +/- 2 and 88 +/- 3 beats/min (p less than 0.02, p less than 0.01, p less than 0.01, respectively) at each dose level. The time taken to develop 1 mm of ST segment depression was prolonged from 4.8 +/- 0.6 minutes during placebo administration to 5.3 +/- 0.7 (p = NS), 6.4 +/- 0.7 (p less than 0.01) and 6.7 +/- 0.8 minutes (p less than 0.001), respectively, at each dose level. The improvement achieved after 2 weeks of nicardipine, 120 mg daily, was maintained over a period of 6 months of follow-up. Three patients were withdrawn, one taking 60 mg of nicardipine, one taking 90 mg of nicardipine and one taking placebo, but the overall incidence of side effects was low. Nicardipine is an effective antianginal agent with an optimal dose of 90 to 120 mg/day.

Adult↗
PubMed1983

The effects of oxprenolol on ambulatory intra-arterial blood pressure in essential hypertension.

Continuous intra-arterial blood pressure recording using the "Oxford" technique has been used to study the antihypertensive effects of oxprenolol taken three times daily in fully ambulatory patients with essential hypertension, outside hospital. During the first 24 h of treatment there was a reduction in daytime heart rate and a small reduction in daytime blood pressure. After 10 weeks treatment there was a more substantial fall in daytime blood pressure from the hour of waking, but no effect on sleeping nighttime blood pressure or heart rate. Twenty-four hour variation, as assessed by the amplitude of a fitted regression curve, showed a reduction in heart rate but not blood pressure variation. In 4 patients restudied after 11 weeks treatment with oxprenolol (tid) and cyclopenthiazide at 9 a.m. there was some evidence of an antihypertensive effect occurring during both the daytime and nighttime.

Adult↗
PubMed1983

Double-blind randomized crossover trial of verapamil and propranolol in chronic stable angina.

Propranolol (240 mg daily) and verapamil (360 mg daily) were objectively compared for their respective efficacy in the treatment of chronic stable angina pectoris. Twenty-two patients were studied in a randomized placebo controlled, double-blind crossover trial with 4 weeks on each active drug treatment. Multistage treadmill exercise with computer-assisted ECG analysis was performed after 2 weeks on placebo and at the end of each 4-week active drug treatment. The mean exercise time to produce angina was 5.5 minutes (SEM +/- 0.4 minutes) on placebo and this increased to 7.8 (+/- 0.5) minutes on propranolol and 9.1 (+/- 0.5) minutes on verapamil. The improvement in exercise time of verapamil over propranolol was statistically significant (p less than 0.01). Ten patients became free of angina with verapamil and four with propranolol. Resting and maximal exercise heart rates were significantly reduced by propranolol; verapamil did not reduce the maximal heart rate but reduced the resting heart rate slightly. However, the heart rate increase per minute of exercise was significantly diminished (p less than 0.001). ST segment changes showed improvement with both drugs despite marked differences in heart rate profile. The overall efficacy of the slow calcium channel blocker, verapamil, compares favorably with that of a standard beta-adrenoreceptor blocking drug (propranolol), thus providing a new perspective in the management of angina pectoris. These two classes of drugs seem to act by different mechanisms and it is suggested that if patients are resistant or intolerant to one of these drugs, the other can be used to yield a beneficial response.

Adult↗
PubMed1983

Objective evaluation of three dose levels of diltiazem in patients with chronic stable angina.

Twenty-one patients with chronic stable angina were treated with the calcium antagonist diltiazem. Dose titration studies involving 180, 270 and 360 mg/day were conducted using a blinded objective protocol. Improvement in exercise tolerance was observed at all dose levels, but the best reduction of anginal attacks and glyceryl trinitrate consumption, enhancement of exercise capacity and improvement of objective ischemic variables were observed with the 360 mg/day dose. The mean exercise time to produce grade II angina on treadmill walking increased from 5.6 +/- 0.7 minutes on placebo to 7.9 +/- 0.8 minutes on diltiazem 180 mg/day (probability [p] less than 0.001), 8.0 +/- 0.8 minutes on 270 mg/day and 9.5 +/- 0.9 minutes on 360 mg/day (p less than 0.001 as compared with 270 mg/day). One patient was withdrawn at the 360 mg/day dosage because of pedal edema. The 24 hour Holter monitoring data confirmed the findings on exercise testing, and left ventricular function was not altered with any dose level. Diltiazem in doses ranging from 180 to 360 mg/day is another powerful antianginal agent in the calcium antagonist group producing excellent therapeutic benefit in chronic stable angina with no adverse effects on left ventricular function.

Aged↗
PubMed1983

Simultaneous recording of continuous arterial pressure, heart rate, and ST segment in ambulant patients with stable angina pectoris.

Simultaneous and accurate recording of arterial blood pressure and ST segment changes is fraught with technical difficulties. We have developed a new system to enable accurate reproduction of the electrocardiogram and intra-arterial blood pressure, using a transducer/perfusion unit conventionally used to study hypertensive subjects, linked to a frequency modulated tape recorder. Detailed methods of digital analysis have been developed to process the data. This system has been used to study 22 patients with arteriographically proven severe obstructive coronary artery disease who suffered frequent attacks of angina. Control data from quantified dynamic exercise in the laboratory were used for comparison with the effects of normal daily activities outside the hospital and to test the hypothesis that "double product" (heart rate X systolic blood pressure) is relevant to the onset of angina in such patients. The most important finding was that both angina and asymptomatic episodes of ST segment depression were invariably accompanied by an increase in heart rate, whereas there was considerable variation in blood pressure changes ranging from an increase to a substantial fall. This suggests that heart rate changes are more important in determining ischaemic episodes than blood pressure. Furthermore, the "double product" was not reproducible during repeated episodes of angina and asymptomatic ischaemia and did not appear to have an important role in the pathogenesis of intermittent myocardial ischaemia in this group of patients.

Aged↗
PubMed1982

Rapid reduction of blood pressure with acute oral labetalol.

1 The effect of acute oral administration of labetalol on intra-arterial pressures in a group of ten hypertensive patients has been evaluated. 2 A single dose of 200 mg labetalol produced a significant reduction in systolic and diastolic pressures within 1 h of administration. 3 Within 24 h of initial administration, 200 mg three times daily produced a significant reduction in ambulant arterial levels of systolic pressure for 21 h and diastolic pressure for 14 h in the day. 4 Acute therapy lowered resting levels but there was no significant reduction in systolic pressure during either isometric or dynamic exercise. 5 Acute therapy was not associated with any significant postural hypotension.

Administration, Oral↗