Prolonged hemodynamic effects (12 hours) of orally administered sustained-release nitroglycerin

Controlled, eight-hour haemodynamic study of a sustained-release formulation of isosorbide dinitrate in moderate left ventricular failure

The aim of the study was to assess the duration of the haemodynamic effects of a new sustained-release oral formulation of isosorbide dinitrate (ISDN). Twenty patients (17 men and 3 women; mean age 60 years) with acute myocardial infarction (10 anterior, 10 inferior) complicated by moderate left ventricular failure took part in a randomized controlled trial. Ten patients were randomly assigned to the placebo group and 10 to the ISDN group, who received 40 mg sustained release isosorbide dinitrate. Haemodynamic variables were measured before treatment, after 0.5 and 1 h and then every 2 hours up to the 8th hour after treatment. There was no significant change in any haemodynamic parameter in the placebo group, during the study period. In the ISDN group there was a significant fall in pulmonary artery diastolic pressure at 4 and 8 h, from 19.0 +/- 1.0 mm Hg to 16.5 +/- 1.2 mm Hg and 15.5 +/- 0.8 mmHg, respectively. The mean pulmonary capillary wedge pressure fell progressively from 17.9 +/- 1.0 to 12.5 +/- 1.2 mmHg at 2 h (p less than 0.001 in comparison with the placebo group. The fall remained significant up to 8 h. There was no statistically significant change in heart rate, cardiac index, systemic blood pressure or systemic and pulmonary vascular resistances. On the whole the cardiac index remained unchanged. There were numerous individual variations of cardiac index in relation to the initial mean pulmonary capillary wedge pressure and the magnitude of its fall following administration of ISDN. The change in cardiac index was inversely correlated with the control cardiac index (r = -0.69, p less than 0.02).

How much of the placebo 'effect' is really statistical regression?

Statistical regression to the mean predicts that patients selected for abnormalcy will, on the average, tend to improve. We argue that most improvements attributed to the placebo effect are actually instances of statistical regression. First, whereas older clinical trials susceptible to regression resulted in a marked improvement in placebo-treated patients, in a modern series of clinical trials whose design tended to protect against regression, we found no significant improvement (median change 0.3 per cent, p greater than 0.05) in placebo-treated patients. Secondly, regression can yield sizeable improvements, even among biochemical tests. Among a series of 15 biochemical tests, theoretical estimates of the improvement due to regression by selection of patients as high abnormals (i.e. 3 standard deviations above the mean) ranged from 2.5 per cent for serum sodium to 26 per cent for serum lactate dehydrogenase (median 10 per cent); empirical estimates ranged from 3.8 per cent for serum chloride to 37.3 per cent for serum phosphorus (median 9.5 per cent). Thus, we urge caution in interpreting patient improvements as causal effects of our actions and should avoid the conceit of assuming that our personal presence has strong healing powers.

The effect of glyceryl trinitrate ointment on heart rate--corrected systolic time intervals in angina pectoris

1 Individual systolic time intervals (STI) v heart rate regression equations were determined using small doses of intravenous atropine in seven patients with angina pectoris. 2 Regression lines of the form LVET = A + B.HR and QS2 = C + D.HR were calculated. There was no significant correlation between PEP and HR. The values of parameters A C and D were significantly different from a group of previously studied normal volunteers. 3 STI changes were recorded for 5 h after the application of GTN or placebo ointment. The active drug caused shortening of LVET and QS2 with the peak effect occurring between 105 and 180 min. After 180 min neither LVET nor QS2 were significantly shortened. There was no significant effect on PEP or heart rate.