Prevention of nifedipine of abnormal coronary vasoconstriction in patients with coronary artery disease

Neuronal control of coronary blood flow

Controversies on acetylcholine-induced increases or decreases in coronary blood flow arise from obvious species differences, the role of endothelium in mediating vascular smooth muscle responses, and the marked negative chronotropic and inotropic effects of acetylcholine. In man, there appears to be a predominant dilation of intact epicardial coronary arteries and a constriction of artherosclerotic segments. However, at present there is no evidence for a vagal initiation of myocardial ischemia. Coronary vascular beta-adrenergic receptors mediate dilation, but appear to be functionally insignificant during sympathetic activation. The beta-adrenergic mechanism contributing to myocardial ischemia are indirect, mediated by a tachycardia-related redistribution of blood flow away from the ischemic myocardium. alpha-Adrenergic receptors mediating epicardial coronary artery constriction in experimental studies appear not to be responsible for the initiation of ischemia in patients with angina at rest. However, alpha-adrenergic constriction of coronary resistance vessels resulting in the precipitation of post-stenotic myocardial ischemia was demonstrated in experimental studies and recently confirmed in patients with effort angina. Non-adrenergic, non-cholinergic neurotransmitters exist; however, their role in regulating coronary blood flow remains entirely unclear.

Noninvasive testing of dynamic component of internal carotid artery stenosis in patients with chronic cerebrovascular disease

By means of Doppler spectral analysis it was shown that internal carotid artery stenosis has a dynamic component that determines the possibility of changes in the area of stenosis under various influences. It was found that the cold pressor test may increase the area of stenosis in some patients for up to three to five hours. In such cases reduction of blood flow volume in the common carotid artery and decrease of cerebral blood flow in the ipsilateral hemisphere of the stenosis are observed. Such a response was effectively removed by nifedipine. At the same time nifedipine itself is capable of changing the area of stenosis, either enlarging or reducing it. In the first case enhancement of brain blood supply is observed, and in the second case, its decrease. The data obtained disclose one of the reasons for the variability in therapeutic effects of vasodilators in patients with cerebrovascular disorders.

A comparison of the acute haemodynamic effects of nisoldipine and nifedipine during treatment with atenolol in patients with coronary artery disease

1. The acute haemodynamic effects of intravenous nisoldipine (1, 2, 4 microg kg(-1)) and nifedipine (2.5, 5, 10 microg kg(-1)) were compared in a randomised, within-patient crossover study. Fifteen male patients with stable angina pectoris treated with atenolol were studied after undergoing routine cardiac catheterisation. 2. Nisoldipine caused a dose-related fall in systemic vascular resistance (maximum 22%) associated with an increase in heart rate and cardiac index (18%) and a fall in mean arterial pressure (7%). 3. By contrast, nifedipine was associated with a significant increase in heart rate but systemic vascular resistance, cardiac index and mean arterial pressure remained unaltered. 4. At doses with equivalent effects on heart rate (2 microg kg(-1) nisoldipine; 10 microg kg(-1) nifedipine) acute dosing with nisoldipine caused a significantly greater fall in systemic vascular resistance and increase in cardiac index, whilst nifedipine caused a greater reduction in stroke volume index and left ventricular stroke work index. 5. The results suggest that, when combined with atenolol, acute dosing with nisoldipine may have a more complementary haemodynamic profile than nifedipine. The implications of this finding for chronic oral dosing in patients with impaired left ventricular function should be evaluated.

Ischemia in collateral-dependent myocardium: effects of nifedipine and diltiazem in man

It has recently been shown that ischemia in collateral-dependent myocardium may develop at a very variable threshold in anginal patients; accordingly, the aim of this study was to assess whether nifedipine and diltiazem can increase blood flow to collateralized myocardium in man. Nine patients with complete coronary occlusion filled by collaterals, with no other coronary stenosis, normal left ventricular function, and reproducibly positive exercise tests were studied. They underwent exercise tests off therapy and after acute randomized administration of nifedipine (10 mg sublingually), diltiazem (120 mg orally), and nitroglycerin (0.5 mg sublingually), the latter a drug known to increase blood flow to collateralized myocardium. Following nifedipine, time to 1 mm ST segment depression increased significantly (from 430 +/- 176 to 576 +/- 205 seconds, p < 0.01), while heart rate and rate-pressure product remained unchanged (115 +/- 16 vs 121 +/- 17 beats/min and 199 +/- 29 vs 204 +/- 44 beats/min.mm Hg.10(2), respectively, p = NS for both). Similarly, diltiazem significantly increased time to ischemic threshold from baseline to 638 +/- 125 seconds (p < 0.01), but did not change heart rate and rate-pressure product at 1 mm ST segment depression. Submaximal rate-pressure products were significantly lowered by both nifedipine and diltiazem. Nitroglycerin not only significantly improved time to ischemic threshold (from baseline to 666 +/- 76 seconds, p < 0.01), but also increased heart rate (from baseline to 137 +/- 16 beats/min, p < 0.01) and rate-pressure product (from baseline to 242 +/- 48 beats/min.mm Hg.10(2), p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Atenolol or nicardipine alone is as efficacious in stable angina as their combination: a double blind randomised trial

BACKGROUND

Beta blockers and calcium antagonists are widely used in the management of angina pectoris in the belief that the combination is more efficacious than either drug alone.

METHODS

This double blind randomised crossover placebo controlled study compares the effects of nicardipine, atenolol and their combination in 30 patients with chronic stable angina. Each treatment period lasted 6 weeks with dose titration after 3 weeks. Symptom limited treadmill exercise testing and radionuclide ventriculography at rest was carried out at the end of each treatment period.

RESULTS

Total exercise duration and time to 1-mm ST-segment depression was significantly prolonged by nicardipine and atenolol when compared to placebo, the combination offered no additional benefit. Time to onset of angina was significantly prolonged by nicardipine and the combination but not by atenolol. Indices of left ventricular function were not significantly affected by any treatment other than an increase in left ventricular end diastolic volume on atenolol and the combination.

CONCLUSIONS

Nicardipine and atenolol are equally effective in prolonging exercise duration and time to onset of ischemia in patients with chronic stable angina while the combination appeared to offer no additional benefit. Nicardipine prolonged the time to onset of angina significantly; again there was no further improvement with the combination. Neither drug appears to have an important effect on the parameters of diastolic function studied in patients with chronic stable angina.

Local and neurohumoral control of coronary blood flow

The powerful local metabolic regulation adjusting coronary blood flow to myocardial oxygen consumption under normal conditions is beyond doubt. However, despite substantial experimental efforts the responsible mediators are still largely unknown. Adenosine, a purported mediator of local metabolic control of coronary blood flow, is probably only involved in transient flow adaptations, but not in steady-state coronary autoregulation. Even below the autoregulatory range a substantial vasodilator reserve persists. Recruitment of such vasodilator reserve results in improved regional myocardial blood flow and attenuated regional ischemic dysfunction. beta-adrenergic coronary dilation is of minor functional importance. alpha-adrenergic coronary constriction acts to attenuate increases in coronary blood flow during sympathetic activation under normal conditions, such that myocardial oxygen extraction increases to match the increased oxygen consumption. alpha-adrenergic coronary constriction remains operative in ischemic myocardium, thus precipitating or contributing to acute myocardial ischemia during sympathetic activation and exercise in experimental animals as well as in patients with stable angina. The vagal transmitter acetylcholine--upon exogenous intracoronary infusion--induces critical constriction of epicardial coronary arteries with endothelial dysfunction and atherosclerosis. However, a vagal initiation of coronary spasm or myocardial ischemia has not been documented so far. Similarly, peptide hormones/transmitters such as NPY, vasopressin, and angiotensin can induce myocardial ischemia upon exogenous administration. Their pathophysiological role in myocardial ischemia and reperfusion, however, remains to be established.

Intravenous nifedipine for prevention of myocardial ischaemia after coronary revascularization

We sought to determine the pharmacokinetic and pharmacodynamic behaviour of a continuous infusion of nifedipine given for prevention of myocardial ischaemia following coronary artery bypass graft (CABG) surgery. Patients scheduled for elective CABG, who had good left ventricular function, were included. Only normotensive patients who did not require treatment with vasoactive drugs and were bleeding less than 100 ml.hr-1 following surgery were included. The patients were randomly distributed into two groups: a control group not receiving any treatment and a treated group receiving a bolus (3 micrograms.kg-1.min-1 for 5 min) and maintenance (0.2 micrograms.kg-1.min-1) infusion of nifedipine, starting upon arrival in the recovery room and continuing for four hours. Patients given nifedipine were compared with control patients in order to determine the effects of nifedipine on haemodynamic function and on the postoperative incidence of hypotension, hypertension, myocardial ischaemia and infarction. Continuous 2-lead Holter monitoring was used to detect myocardial ischaemia. Infarction was diagnosed by 12-lead ECGs and by assessment of the MB-isoenzyme creatine kinase. The infusion of nifedipine rapidly achieved and maintained plasma concentrations between 30 and 40 ng.ml-1. The pharmacokinetic studies revealed a systemic clearance of nifedipine of 0.371 +/- 0.101 L.hr-1.kg-1, an apparent volume of distribution of 0.764 +/- 0.288 L.kg-1 and an elimination half-life of 1.4 +/- 0.6 hr. No correlation was found between plasma concentration of nifedipine and mean arterial pressure (MAP). The incidence of postoperative hypotension (MAP < 70 mmHg) and hypertension (MAP > 100 mmHg) was comparable between the groups. All haemodynamic variables were similar in both groups during the study period. Of 23 patients who received nifedipine, none showed evidence of ischaemia within six hours of starting the infusion. During the same period, five of 24 patients in the control group had ST-segment deviation suggestive of myocardial ischaemia (P = 0.05, Fisher's exact test). Three patients in the control group and none in the nifedipine group suffered perioperative myocardial infarction (P = NS). In conclusion, the continuous infusion of nifedipine used in this study is safe and reduces the incidence of myocardial ischaemia in normotensive patients with good left ventricular function following CABG. Further studies of larger number of patients are required to determine the role of calcium entry blockers following coronary artery surgery.

Daily life ischemia and nitrate therapy

Daily life ischemia has generated considerable interest because most of it is silent and associated with increased risk of adverse outcome. Coronary vasomotion, as well as increases in myocardial oxygen demand, seem important in the pathogenesis of this form of ischemia, so treatment with nitrates seems rational. Administration of sublingual nitroglycerin hourly, over 12 hours, was shown to decrease both silent and painful ischemic episodes in patients with effort angina. Subsequently, isosorbide dinitrate or mononitrate, given either as an intravenous infusion or orally, was shown to decrease both silent and painful ischemic episodes in patients with unstable rest angina and in those with severe angina. More recently, 6 studies have reported using transdermal nitroglycerin for daily life ischemia. Three of these reported open-label uncontrolled observations and suggested that ischemia frequency may be reduced approximately 60-80% during treatment with doses of 10-30 mg/day, with a duration of treatment ranging from 1 hour to 14 days. In 2 of these reports the duration of ischemia also decreased. The other 3 studies were randomized, double-blind, placebo-controlled studies with a total enrollment of 86 patients. These studies provided mixed results. One suggested that evidence for partial tolerance develops within 1 day of treatment, using large continuous or intermittent doses (mean, 52 mg/day). Another suggested that no tolerance develops to intermittent dosing (18 mg/16 hr out of 24 hr) during exercise testing but no effect is seen on daily life ischemia. The remaining study suggested that tolerance does not develop using small doses (15 mg/day) continuously over 14 days for ischemia during daily life, and that this response is different from that observed using the calcium antagonist nifedipine. These limited observations and conflicting results underscore a need for additional larger controlled trials, employing topical nitrate therapy in low intermittent doses for daily life ischemia.

Optimal control of myocardial ischaemia: the benefit of a fixed combination of atenolol and nifedipine in patients with chronic stable angina

OBJECTIVE

To study the effects on myocardial ischaemia of 50 mg of atenolol, 20 mg of slow release nifedipine, and their fixed combination given 12 hourly.

DESIGN

A treadmill exercise test and 24 hour ambulatory electrocardiographic monitoring were carried out after a period of five days off treatment (control) and at the end of three weeks of each treatment period.

PATIENTS

23 patients with stable angina pectoris, documented coronary artery disease, and a positive exercise test were randomised in a double blind, three way, cross over study.

RESULTS

Compared with the control, nifedipine significantly induced an increase in resting heart rate of (mean (SEM)) 14 (2) beats/min whereas atenolol and the combination significantly reduced it by 24 (2) and 20 (1) beats/min respectively. The number of exercise tests rendered negative after each intervention was five for nifedipine, nine for atenolol, and 11 for the combination. Compared with the control the time to the start of myocardial ischaemia (1 mm ST segment depression) during exercise significantly increased by 3.2 (0.6) min after nifedipine, by 4.6 (0.4) min after atenolol, and by 4.6 (0.5) min after the combination; rate-pressure product (beats/min. mm Hg) at 1 mm ST segment depression increased by 2824 (970) after nifedipine but fell by 4436 (900) and 4501 (719) after atenolol and the combination. The weekly frequency of angina was reduced from a mean of five while taking nifedipine, to three while taking atenolol, and to two while taking the combination. The total ischaemic time during ambulatory monitoring was significantly reduced from 69 (17) min during control to 37.5 (9.8) min during nifedipine, to 15.6 (5.5) min during atenolol, and to 6.5 (2.7) min during the combination.

CONCLUSION

The undesirable effect of a high basal heart rate induced by nifedipine was neutralised by its combination with atenolol. Whereas atenolol and the combination were equally efficacious in controlling exercise induced ischaemia, the combination was more effective in reducing total ischaemic burden.

Heterogeneous interference of nicardipine, verapamil, and diltiazem with forearm arteriolar responsiveness to adrenergic stimulation in hypertensive patients

The interference of intraarterial nicardipine, verapamil, and diltiazem with the forearm vascular response to graded exogenous norepinephrine was evaluated in hypertensive patients. Nicardipine antagonized the vasoconstrictor effect of norepinephrine in a dose-dependent manner, whereas verapamil was ineffective, suggesting that functional alpha-adrenergic antagonism may participate in the vasodilatory and possibly the antihypertensive effect. Nicardipine also blunted the vasoconstriction to lower-body negative pressure and the action of angiotensin II administered intraarterially. Despite a comparable increase in basal forearm flow, verapamil was less potent than nicardipine in inhibiting vasoconstriction after both stimuli. Therefore nicardipine suppressed preferentially regional vascular reactivity, probably by blockade of the influx of extracellular calcium in response to receptor activation, because both alpha-adrenergic and angiotensin II receptor-mediated vasoconstrictor responses were attenuated. At variance with both nicardipine and verapamil was potentiation of the responses to norepinephrine after the administration of diltiazem. Because intraarterial propranolol abolished that potentiating action and the local vasodilatation to isoproterenol was clearly reduced, diltiazem probably interfered also with beta-adrenergic receptor-mediated vasorelaxing mechanisms in human forearm arterioles. The data further stress the heterogeneity of calcium channel blockers in humans.

Randomized double-blind comparison of isosorbide dinitrate and nifedipine in variant angina pectoris

The antianginal and anti-ischemic effect of isosorbide dinitrate (ISDN), 120 mg once daily, and nifedipine, 20 mg twice daily, both in slow-release formulations, were compared in 17 patients with variant angina pectoris in a randomized, double-blind trial. The design included a placebo run-in period and two 6-week crossover periods of active treatment. Mean frequency of angina decreased significantly from 43 attacks per week during the placebo period to 4 per week with ISDN and 8 with nifedipine (p less than 0.001). Sublingual nitroglycerin consumption decreased significantly from 37 tablets per week with placebo to 3 tablets per week with ISDN and 7 with nifedipine (p less than 0.001). Both drugs reduced the silent and symptomatic ST-segment deviations on ambulatory electrocardiographic recording and increased maximal exercise tolerance. Episodes of coronary spasm could be provoked, by hyperventilation, in all patients during the placebo phase but in no patient during therapy with either active drug. Thus, both ISDN and nifedipine, in their slow-release formulations, are effective in the treatment of variant angina pectoris.

Raised plasma endothelin-I concentration following cold pressor test

Plasma concentration of immunoreactive endothelin-1 was measured by radioimmunoassay in 6 healthy subjects before and following cold pressor test by immersion of one fore-arm into ice-water. Mean (SEM) plasma endothelin-1 concentration rose from 1.2 (0.7) to peak value 8.4 (2.3) pg/ml in venous plasma from the immersed hand, and, reaching peak 2 minutes later, from 1.4 (0.5) to 4.6 (2.3) pg/ml in venous plasma from the contralateral hand. In 66 healthy control subjects, venous plasma concentration of endothelin-1 was 2.9 +/- 1.2 pg/ml (mean +/- SD). Exposure to cold is associated with raised blood levels of endothelin-1, which points to a relation between endothelin-1 and vasoconstriction associated with low temperature.

Effects of nifedipine on myocardial perfusion during exercise in chronic stable angina pectoris

Nifedipine may be effective in the treatment of stable angina by both decreasing myocardial oxygen demand and increasing myocardial oxygen supply. To determine the mechanism of action of nifedipine and its dose-response relation, 14 patients with stable angina were treated with nifedipine 10, 20 and 30 mg 4 times daily as single-agent therapy in a double-blind, randomized, placebo-controlled crossover trial. Treatment was continued for 1 week on each dose regimen and efficacy was determined using an exercise test at the end of each phase. Compared to placebo, a significant decrease of systolic blood pressure at peak exercise occurred with the nifedipine 20- and 30-mg regimens (p less than 0.05), accompanied by an increase in heart rate on the 10- and 20-mg regimens (p less than 0.005). There was no significant effect on the rate-pressure product compared to placebo at any exercise time on any of the nifedipine regimens. The times to onset of ST-segment depression and to angina were delayed significantly by all 3 dose regimens compared to placebo (p less than 0.02). There was a significant decrease in the magnitude of ST-segment depression at all exercise times by all dosage schedules of nifedipine compared with placebo (p less than 0.05), although there were no significant differences among the 3 dosage schedules. Data indicate that since nifedipine was effective in improving manifestations of myocardial ischemia during exercise without altering the double product at submaximal or maximal exercise, its beneficial mechanism of action may have been due to enhancing blood flow to ischemic zones or to favorably altering determinants of myocardial oxygen demand, which were not measured.

Superior efficacy of propranolol versus nifedipine in double-component angina, as related to different influences on coronary vasomotility

PURPOSE

In 24 patients with stable spontaneous and effort-related angina, ischemic episodes at rest were not preceded by changes in circulatory variables (heart rate, systemic and pulmonary arterial pressures) that may raise the myocardial oxygen consumption. We interpreted these episodes as caused by critical and reversible coronary flow reduction at the site of a stenotic lesion, and evaluated the clinical efficacy of nifedipine and propranolol in the treatment of this condition.

PATIENTS AND METHODS

The study was randomized, placebo-controlled, and crossover in design. Nineteen of the 24 subjects were men (mean group age, 59 years; range, 47 to 65 years). The study consisted of four four-day periods. The first and the fourth periods, during which patients received placebo, were single-blind. The treatment consisted of 80 mg of propranolol or 20 mg of nifedipine administered four times daily. The second and the third periods, during which patients received propranolol or nifedipine crossing over to the alternative drug in the next period, were double-blind and separated by a 24-hour interval.

RESULTS

Propranolol fully abolished or reduced the number of spontaneous ischemic episodes in a significantly larger proportion of patients than did nifedipine; it was also effective in several cases in which nifedipine had failed or had even caused a paradoxic effect. Quantitative angiographic evaluation of the influences of nifedipine (Group 1, 12 patients, 10 mg sublingually) and propranolol (Group 2, 12 patients, 0.1 mg/kg intravenously) on the residual lumen diameter of one significant coronary stenosis in each patient showed that (1) after nifedipine, the lumen was unchanged in one, augmented in seven, and reduced in four cases; (2) variations ranged between +1.59 and -1.2 mm, and their direction correlated closely with the influence of oral nifedipine on the episodes of spontaneous ischemia; and (3) in no case did treatment with propranolol vary the stenosis lumen by more than 0.3 mm.

CONCLUSION

In this form of angina, a number of lesions seem to offer a compliant substrate for vasomotion and, possibly, for critical changes in flow. The vasomotor influences of nifedipine on these lesions are variable as well as the efficacy of the drug on the manifestations of ischemia at rest. Propranolol produces no important variations of the coronary stenotic lesions, causes a decrease of heart rate that facilitates coronary flow in diastole, and reduces the baseline metabolic demand of the heart so that the threshold of ischemia during critical reduction of coronary flow may become elevated.

Antivasoconstrictor effects of isradipine. A quantitative approach in anesthetized rats and conscious rabbits

Calcium antagonists blunt the constrictor effects of vasoconstrictor agents. Differences in the sensitivity of several vasoconstrictors to the constrictor effect of calcium antagonists were quantified in experiments on rats and rabbits. In rats, the dose-response curves for pressor effects to angiotensin II were shifted in parallel to the right after treatment with isradipine, but not with prazosin and dihydralazine, suggesting that the antivasoconstrictor effect of isradipine was of a specific type. Blood pressure increases elicited by angiotension II or norepinephrine (alone, or with propranolol or propranolol plus prazosin) were also measured in rabbits and, again, isradipine caused parallel shifts of the dose-response curves. Both agonists thus appear to stimulate calcium entry, at least in resistance vessels, and via the same pathway, the L-type calcium channel. However, the angiotension II pressor effects were more sensitive to isradipine than those of norepinephrine in the presence of propranolol, and even more so in the presence of propranolol plus prazosin. These results suggest subtle and as yet unexplained differences, possible related to the activity of the adenylate cyclase system, in the chain of events leading to activation of the L-channels in vivo.

Pharmacological mechanisms to attenuate sympathetically induced myocardial ischemia

Distal to a coronary stenosis, resting myocardial blood flow and function can be maintained by a compensatory dilation of the poststenotic vascular bed and an increased collateral blood flow from adjacent coronary vessels. Under this condition, electrical stimulation of cardiac sympathetic nerves, as well as their activation during sympathoexcitatory reflexes and exercise, induces a poststenotic alpha 2-adrenoceptor-mediated coronary constriction and a beta-adrenoceptor-mediated, tachycardia-related redistribution of blood flow away from the ischemia myocardium. Thus, activation of cardiac sympathetic nerves can precipitate poststenotic myocardial ischemia. In experimental studies in anesthetized, vagotomized dogs, as well as in conscious, chronically instrumented dogs, selective alpha 2-adrenoceptor antagonists and calcium-channel blockade with nifedipine were able to attenuate the sympathetically induced poststenotic myocardial ischemia. Beta-adrenoceptor blockade with atenolol was only proven beneficial as long as there was a heart-rate reduction. Conversely, a specific bradycardic agent (ULFS-49) also exerted beneficial effects. Myocardial ischemia can activate cardiac sympathetic afferents and then, by a spinal reflex, can in turn activate sympathetic efferents and aggravate the severity of myocardial ischemia. This vicious cycle could be interrupted by segmental epidural anesthesia with procaine as well as by blockade of sympathoexcitation at the central nervous level with clonidine in anesthetized dogs.

Different coronary vasomotor effects of nifedipine and therapeutic correlates in angina with spontaneous and effort components versus Prinzmetal angina

Flow impedance, probably of vasomotor origin, superimposed on severe coronary stenosis has been considered a trigger for the spontaneous component of angina occurring both on effort and at rest. To investigate more thoroughly this pathophysiologic aspect we evaluated (by means of quantitative coronary angiography) the acute vasomotor reaction to nifedipine (10 mg sublingually) of significant (greater than 50%) stenotic lesions in 22 patients with double-component angina. We also correlated this reaction with the clinical response (daily number of ischemic episodes evaluated by means of 48-hour Holter ambulatory monitoring) to treatment with nifedipine (20 mg four times a day); calcium channel blockade, in fact, is considered a specific remedy in cases of altered coronary vasomotility. Patients with Prinzmetal angina, who were known to have homogeneous coronary vasodilating reactions and favorable clinical responses to nifedipine, were studied by means of the same methods and served as the control group (14 patients). In double-component angina the residual lumen diameter of significant lesions was unchanged in two patients, enhanced in 10, and reduced in 10 after sublingual nifedipine; lumen variations from baseline values ranged from +1.29 to -1.56 mm. Acute changes in stenosis correlated closely with results obtained with oral treatment. In the group with Prinzmetal angina, coronary stenoses invariably responded with dilatation (the residual coronary lumen increased by an average of 69% of baseline); 100% of the patients in this group responded favorably to treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Chronic stable angina monotherapy. Nifedipine versus propranolol

A placebo-controlled, double-blind, crossover study was conducted to determine the effects of nifedipine (60 to 90 mg per day) monotherapy and propranolol (240 mg per day) monotherapy on symptoms, angina threshold, and cardiac function in patients with chronic stable angina. Following a two-week placebo period, patients were randomly assigned to receive either nifedipine or propranolol for a five-week treatment period, after which they crossed over to the alternative regimen. All 21 patients were men with chronic stable angina pectoris, 13 of whom had symptoms both at rest and on exertion. New York Heart Association functional class improved in patients taking either nifedipine or propranolol, and nitroglycerin consumption decreased with both treatments compared with placebo. Nifedipine significantly delayed the onset of chest pain and 1 mm of ST-segment depression during bicycle exercise; increases with propranolol were smaller and not statistically significant. Nine patients had a preferential clinical response to nifedipine compared with six patients to propranolol; this was unrelated to the presence or absence of pain at rest or to any baseline hemodynamic finding. Nifedipine and propranolol were equally effective in relieving exertional ischemia as shown by improvement in radionuclide ejection fraction at identical work loads. Exercise wall motion, assessed by a semiquantitative wall motion score, also improved with both drugs. Propranolol treatment decreased exercise cardiac output by 14 percent (p = 0.01) through its effect on heart rate. In contrast, nifedipine treatment had no effect on cardiac output. Thus, nifedipine is more effective on several measurements than propranolol when administered as single drug therapy in stable angina and has the advantage of preserving cardiac output during exercise.

Coronary collateral reserve during exercise induced ischemia in swine

We determined coronary collateral vasodilator reserve during exercise-induced ischemia in 17 mini-swine. We induced coronary collateral development in the left circumflex bed by placing an ameroid occluder on that artery. Four weeks later we studied the animals at rest and during exercise (EX) eliciting heart rates (HR) of 240 and 265 beats/min. We measured myocardial blood flow with microspheres and myocardial function by wall thickness sonomicrometry gauges. At matched exercise HRs we treated the animals with nifedipine (10 micrograms/kg IV) (EXN 10), nifedipine (100 micrograms/kg IV), (EXN 100), and adenosine infusion (1.2 mg/min/kg) EXAD. EXN 10 did not significantly alter hemodynamics compared to EX but EXN 100 and EXAD both decreased blood pressure significantly (p less than 0.05). Ischemic endocardial/nonischemic endocardial flow ratios and collateral resistance served as indices of vasodilator reserve. In the ischemic zone exercise reduced vasodilator reserve to 24 +/- 3% in the endocardium and 64 +/- 7% in the epicardium. Neither EXN 10 nor EXAD improved exercise-induced ischemia measured either as flow or function. However EXN 100 improved function during exercise-induced ischemia without improving coronary collateral flow. We conclude there is no additional coronary flow reserve during exercise-induced ischemia in the collateral dependent bed of the pig a few days after occlusion that can be recruited. Large doses of nifedipine improve function by direct action on the myocardium or by reducing afterload. The lack of development and deep myocardial distribution of the coronary collateral vessels in the pig may be an important factor of why these nifedipine responses differ from those reported in species which have primarily large epicardial coronary collaterals.

[Calcium inhibitors and anesthesia]

Calcium blockers (CB) are routinely used. This could lead to possible interference with anaesthetic drugs. CB prevent calcium from entering the cell by inhibiting the slow voltage-dependent calcium channels. They act mostly on heart and smooth muscle. Of all the possible indications, the three that are confirmed are coronary heart disease, arterial hypertension and supraventricular rhythm disturbances. Most of the work published and the cases reported concerns interactions between CB and halogenated anaesthetic agents; the latter's actions on the heart depend on cellular calcium exchange. Also, the cardiovascular effects of these anaesthetics are similar to that of CB. Experimentally, halothane and enflurane have direct cardiac inhibitory effects similar to verapamil and diltiazem, whereas isoflurane's properties seem closer to the dihydropyridines (nifedipine and nicardipine). Giving verapamil or diltiazem increases the number of sino-atrial and atrio-ventricular blocks when using a halogenated agent. Clinically, interpreting the effects of CB during anaesthetic induction is difficult because of the pathology (coronary heart disease, cardiac failure), the other drugs (beta-blockers and nitrates) and the type of anaesthesia (emergency or elective). Interactions can give rise to anything from a severe cardiovascular collapse, requiring catecholamines, to a mild fall in blood pressure which responds well to plasma expansion, or even no effect on blood pressure. Rebound is seen on stopping CB in patients with coronary heart disease or arterial hypertension; stopping them before surgery does not therefore seem justified. However, extreme care must be taken when using halogenated agents for patients under treatment with CB and/or beta-blockers. A wary anaesthetist will be able to adapt the technique to the patient. It has been suggested that CB could be used to treat preoperatively myocardial ischaemia (diltiazem), hypertensive crises (nifedipine, nicardipine) and ventricular rhythm disturbances (verapamil); this must be done with caution, the patient being closely monitored (haemodynamic and electrocardiographic monitoring). Postoperatively, intranasal nifedipine, continuous intravenous nicardipine or diltiazem have been used to treat increases in arterial blood pressure during recovery and to adapt the cardiovascular system to the increased metabolic needs. Here again, close patient monitoring is essential. In any case, treatment with CB which has been stopped should be started up again as soon as possible.

Delayed myocardial ischemia following the cessation of sympathetic stimulation

A phenomenon entitled "delayed myocardial ischemia" has been described, in which there is a significant degree of coronary malperfusion following the cessation of behavioral stress. The primary objective of the present study was to develop a model for the delayed ischemic response in anesthetized animals to gain insights into the underlying mechanisms. In 15 morphine and chloralose-anesthetized dogs, a moderate degree of stenosis was applied to the left circumflex coronary artery by means of a toroidal balloon occluder. The pulsed Doppler technique was used to monitor coronary flow. After baseline data were obtained, the left stellate ganglion was stimulated for 30 seconds. Heart rate increased (63%), as did systemic blood pressure (41%) and flow in the left circumflex artery (47%). These parameters rapidly returned to control levels when stimulation was terminated. Forty-five to 90 seconds later, coronary flow decreased by 65% and coronary vascular resistance increased by 45%. These hemodynamic changes were accompanied by ECG abnormalities indicative of regional myocardial ischemia. The delayed ischemic response could be prevented by pretreatment with either nifedipine (20 micrograms/kg) or prazosin (0.3 mg/kg). These data indicate that the primary mechanism for the delayed ischemic response is alpha-adrenergically mediated contraction of the smooth muscle in the coronary artery wall.

Total ischemic burden: effect of vasoactive agents

Treatment of the total ischemic burden is dependent on adequate documentation of both painful and painless episodes of myocardial ischemia, an understanding of the pathophysiologic mechanisms involved, and knowledge of prognosis for affected patients. Because a vasoconstrictive component appears to be an important element in the genesis of many episodes of myocardial ischemia, those vasoactive drugs that produce increased flow in the coronary circulation should be clinically useful. Nitrates and calcium blockers--especially nifedipine--have been found to be particularly valuable in this regard in both experimental and clinical trials.

Asymptomatic myocardial ischemia following cold provocation

Cold is thought to provoke angina in patients with coronary disease either by an increase in myocardial demand or an increase in coronary vascular resistance. We investigated and compared the effects of cold pressor stimulation and symptom-limited supine bicycle exercise on regional myocardial perfusion in 35 patients with stable angina and coronary disease and in 10 normal subjects. Regional myocardial perfusion was assessed with positron emission tomography and rubidium-82. Following cold pressor stimulation 24 of 35 patients demonstrated significant abnormalities of regional myocardial perfusion with reduced cation uptake in affected regions of myocardium: 52 +/- 9 to 43 +/- 9 (p less than 0.001 vs normal subjects). Among these 24 patients only nine developed ST depression and only seven had angina. In contrast, 29 of 35 patients underwent supine exercise, and abnormal regional myocardial perfusion occurred in all 29, with a reduction in cation intake from 48 +/- 10 to 43 +/- 14 (p less than 0.001 vs normal subjects). Angina was present in 27 of 29 and ST depression in 25 of 29. Although the absolute decrease in cation uptake was somewhat greater following cold as opposed to exercise, the peak heart rate after cold was significantly lower than that after exercise (82 +/- 12 vs 108 +/- 16 bpm, p less than 0.05). Peak systolic blood pressures after cold and exercise were similar (159 +/- 24 vs 158 +/- 28). Thus, cold produces much more frequent asymptomatic disturbances of regional myocardial perfusion in patients with stable angina and coronary disease than is suggested by pain or ECG changes.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of nifedipine and isosorbide dinitrate when added to maximal propranolol therapy in stable angina pectoris

A study was performed to compare isosorbide dinitrate and nifedipine as adjunctive therapy in 14 patients with coronary artery disease and stable angina pectoris taking maximal beta-blocking drugs. Drug titration phases ensured maximal therapy of propranolol, isosorbide or nifedipine. The combination of nifedipine and propranolol was more effective than the combination of isosorbide and propranolol in reducing angina and increasing exercise capacity (323 vs 416 seconds, p less than 0.005) during exercise treadmill testing. Nifedipine produced a greater reduction in systolic blood pressure at submaximal exercise than isosorbide. Global and regional ejection fraction at rest and exercise was assessed with radionuclide ventriculography. The substitution of nifedipine for isosorbide depressed the global ejection fraction at rest (0.61 to 0.56 p less than 0.05) and produced a slight improvement in exercise ejection fraction (0.47 to 0.51, difference not significant). The decrease in ejection fraction from rest to exercise was 0.14 to 0.04 with nifedipine (p less than 0.005). The benefit of nifedipine compared with isosorbide occurred in regions with marked exercise-induced ischemia. In patients treated with maximal beta-blocking therapy, nifedipine is an effective alternative to isosorbide as a combination agent with propranolol. The salutary effects of nifedipine included afterload reduction with exercise and possible improvements in coronary blood supply.

Selective effects of PN 200-110 (isradipine) on the peripheral circulation and the heart

PN 200-110 (isradipine) is a new dihydropyridine calcium antagonist with selective actions on the heart as well as the peripheral circulation. It selectively inhibits the sinus node but not atrioventricular conduction and its negative inotropic action is minimal, about 20 times weaker than its negative chronotropic effect. This in vitro pattern also expresses itself in vivo: partial suppression of the reflex tachycardia induced by its peripheral vasodilatation and no effect on the P-Q interval on the electrocardiogram even at large doses. The presence of first- or second-degree heart block should therefore not limit its use, whereas the sick sinus syndrome might. PN 200-110 does not decrease myocardial contractile force even in vagotomized animals with full beta blockade. PN 200-110 nevertheless lowers myocardial oxygen consumption mainly by its action on afterload. It should therefore be useful in angina pectoris. PN 200-110 is a powerful peripheral vasodilator. It preferentially dilates coronary, cerebral and skeletal muscle vasculature. Its long lasting (24 to 48 hours) antihypertensive action is not accompanied by tachycardia in spontaneously hypertensive rats and it enhances sodium and water excretion in normotensive rats. It should be useful in the treatment of hypertension, and, considering its pattern of cardiac actions, perhaps also as an after-load-reducing agent for the treatment of heart failure. Antiarteriosclerotic effects in conscious rabbits were found at reasonably small doses, suggesting that such effects might occur in man at therapeutic doses.

Calcium antagonists for Prinzmetal's variant angina, unstable angina and silent myocardial ischemia: therapeutic tool and probe for identification of pathophysiologic mechanisms

The calcium antagonists provide a unique tool to reduce myocardial oxygen demand and prevent increases in coronary vasomotor tone. For patients with Prinzmetal's variant angina, diltiazem, nifedipine and verapamil are extremely effective in preventing episodes of coronary vasospasm and symptoms of ischemia. Unstable angina pectoris is a more complex pathophysiologic syndrome with episodes of ischemia due to increases in coronary vasomotor tone, intermittent platelet aggregation or alterations in the underlying atherosclerotic plaque. Each of the calcium antagonists is effective as monotherapy in decreasing the frequency of angina at rest. Nifedipine is the only calcium antagonist that has been studied in a combination regimen with beta blockers and nitrates for patients with unstable angina, and control of angina is better with the combination regimen than with either form of therapy alone. Although symptoms of myocardial ischemia in unstable angina are reduced by calcium antagonists, these agents do not seem to decrease the incidence of adverse outcomes. Antiplatelet therapy appears to improve morbidity and mortality in patients with unstable angina, suggesting that thrombus formation may play a central role in that disorder. Episodes of silent or asymptomatic myocardial ischemia, identified by ST-segment monitoring, occur in a variety of disorders of coronary disease. Among patients with Prinzmetal's variant angina and unstable angina, episodes of silent ischemia appear to be as frequent as episodes of angina and the calcium antagonists are effective in decreasing episodes of ischemia regardless of the presence or absence of symptoms. Persisting episodes of silent ischemia among patients with unstable angina despite maximal medical therapy identify patients at high risk for an early unfavorable outcome. Among patients with stable exertional angina, episodes of silent ischemia may be up to 5 times as frequent as episodes of angina, and may be due to increases in coronary vasomotor tone, transient platelet aggregation or increases in myocardial oxygen demand. Preliminary experience suggests that calcium antagonists and beta blockers are effective in decreasing episodes of silent ischemia in patients with stable exertional angina and that a combination regimen may be more effective than either form of therapy alone.

Alternative medical treatment for patients with angina pectoris and adverse reactions to beta blockers. Usefulness of nifedipine

Although beta blockers are effective for the treatment of angina pectoris, chronic adverse effects produced by these agents--including lethargy, fatigue, and male impotence--can adversely affect patient acceptance and treatment compliance. To assess the clinical effects of switching from anti-anginal treatment with beta blocker only (phase I) to half-dose beta blocker plus the calcium blocker nifedipine (phase II) or nifedipine alone (phase III), 18 patients with chronic stable angina pectoris and side effects to beta blockers were evaluated in a 12-week, open-label trial. Three patients did not complete the study, one secondary to new unstable angina and two secondary to nifedipine side effects. Of the 15 patients completing the trial (13 men and two women; mean age, 54 +/- 5 [SEM] years), all sequentially participated in the one-month phases. Weekly angina frequency assessed from patient diaries was significantly less for treatment with nifedipine only (phase III) as compared with beta blocker (phase I) (1.7 +/- 1 versus 3.9 +/- 1 episodes per week), while phase II was not significantly different. Exercise test time was maintained throughout all phases (phase I, 457 +/- 39; phase II, 458 +/- 40; and phase III, 498 +/- 48 seconds, p not significant). All 15 patients in phase I (100 percent) had side effects to beta blockers, but these side effects were lessened in 12 patients (80 percent) in phase II and 13 patients (86 percent) in phase III, with total alleviation of symptoms in two patients (13 percent) in phase II, and eight patients (53 percent) in phase III. Thus, in patients with side effects to beta blockers, switching to nifedipine is associated with a significant reduction in beta blocker adverse symptoms and equal anti-anginal efficacy.

The haemodynamic effects of nifedipine, verapamil and diltiazem in patients with coronary artery disease. A review

Of the 3 most widely used calcium antagonists--nifedipine, verapamil and diltiazem--nifedipine is the most potent arterial vasodilator. Increases in cardiac output and coronary blood flow following nifedipine administration result in part from the afterload reduction. Reflex adrenergic stimulation produces an increase in heart rate and masks a direct inhibitory effect on myocardial contractility. The negative inotropic action of nifedipine is observed during intracoronary administration or may be made apparent by concurrent beta-blocker therapy. While verapamil is also a potent vasodilator, negative inotropic and dromotropic properties are more apparent in therapeutically used dosages. Reflex sympathetic activation is also triggered by verapamil, with an offsetting of the negative inotropic effects such that little change in cardiac output results. A decrease in myocardial oxygen consumption, with or without a decrease in coronary sinus blood flow, has regularly been observed following verapamil administration. Reduced oxygen demand appears to be a major mechanism of its antianginal effect. The heart rate X systolic pressure product is decreased both by the fall in arterial pressure and, particularly after oral administration, by a decrease in heart rate. Diltiazem produces similar haemodynamic and electrophysiological effects to those of verapamil but has less potency in inducing arterial dilatation and more of a tendency to slow the heart rate. Diltiazem does not appear to cause significant increases in coronary blood flow or bring about improvement in ejectional and isovolumic indices of myocardial contraction - evidence of its intrinsic negative inotropic effect.

Comparison of nifedipine alone with propranolol alone for stable angina pectoris including hemodynamics at rest and during exercise

The effects of nifedipine (60 to 90 mg/day) and propranolol (240 mg/day) on symptoms, angina threshold and cardiac function were compared in a placebo-controlled, double-blind, crossover study. Five-week treatment periods with nifedipine and propranolol were compared with 2 weeks of placebo treatment in 21 men with chronic stable angina pectoris, 13 of whom had symptoms both at rest and on exertion. Compared with placebo, New York Heart Association functional class improved in patients equally with nifedipine (p = 0.001) and propranolol (p = 0.006). Frequency of chest pain decreased with nifedipine (p = 0.001) and propranolol (p = 0.01), and nitroglycerin consumption similarly decreased with both treatments. Nifedipine significantly delayed the onset of chest pain (p = 0.01) and 1 mm of ST-segment depression (p = 0.002) during bicycle exercise; smaller increases with propranolol were not statistically significant. A preferential clinical response to nifedipine (9 patients) or propranolol (6 patients) was unrelated to the presence or absence of pain at rest or to any baseline hemodynamic finding. Nifedipine and propranolol were equally effective in relieving exertional ischemia as shown by improvements in ejection fraction at identical workloads, from 0.48 +/- 0.11 to 0.58 +/- 0.12 (p less than 0.001) and 0.56 +/- 0.14 (p less than 0.001), respectively. Exercise wall motion, assessed by a semiquantitative wall motion score, also improved with both drugs. Propranolol treatment decreased exercise cardiac output by 14% (p = 0.01) through its effect on heart rate. In contrast, nifedipine treatment had no effect on cardiac output.(ABSTRACT TRUNCATED AT 250 WORDS)

Double-blind crossover comparison of the antianginal effects of nifedipine and isosorbide dinitrate in patients with exertional angina receiving propranolol

A double-blind crossover study was performed on 27 patients with proved fixed coronary artery disease and stable angina pectoris. The study was designed to compare the relative efficacy of two combination therapies, nifedipine plus propranolol and isosorbide dinitrate plus propranolol, in terms of antianginal response and effect on exercise tolerance by evaluation of treadmill testing. The combination of nifedipine and propranolol was superior to the combination of isosorbide and propranolol in reducing the number of anginal attacks (p = 0.03), increasing total exercise time (p less than 0.02), increasing oxygen consumption achieved at end of exercise (p less than 0.03), increasing time to onset of pain (p = 0.003) and increasing oxygen consumption achieved at onset of pain (p = 0.003). Analysis of the rate-pressure products suggests that the difference in these results may be explained by the greater effect of nifedipine on afterload reduction. Although nitroglycerin consumption was reduced from baseline levels during combination nifedipine therapy (p less than 0.001), there was no statistical difference between nifedipine combination therapy and isosorbide combination therapy. In conclusion, although both combination therapies were superior to propranolol therapy alone, the combination of nifedipine and propranolol was more effective than the combination of isosorbide and propranolol in reducing the incidence of angina and improving exercise performance. Side effects were experienced at a similar frequency during both combination therapies.

Regional coronary vasoconstriction after combined beta-adrenergic and calcium channel blockade in patients with coronary artery disease

The beta-adrenergic and calcium channel blocking drugs, which individually and combined have proven efficacious in the treatment of angina pectoris, appear to have opposing effects on coronary artery vasomotion. Previous studies have shown that beta-adrenergic blockade may potentiate and calcium channel blockade reverse coronary vasoconstriction during adrenergic cold stimulation in patients with coronary artery disease. To assess the coronary hemodynamic effects of combined drug therapy, thermodilution coronary sinus and great cardiac vein flow and mean arterial pressure were measured during serial cold pressor testing, both before and after 0.1 mg/kg of intravenous propranolol and again after the addition of 10 mg of sublingual nifedipine in 21 patients (9 without [group A1] and 12 with [group A2] greater than 50% narrowing of the left anterior descending coronary artery). In an additional 15 patients (6 patients without [group B1] and 9 with [group B2] left anterior descending artery stenosis), serial cold pressor testing was performed reversing the drug order. Despite significant increases in mean arterial pressure (p less than 0.01) during cold pressor testing, coronary sinus resistance responses after propranolol plus nifedipine were not statistically significant for any group. However, regional coronary resistance responses differed between patients with and without left anterior descending artery stenosis. In group A1, great cardiac vein resistance was unchanged after propranolol plus nifedipine. In group A2, great cardiac vein flow decreased significantly after propranolol plus nifedipine from 8 +/- 17 to -4 +/- 12% (p less than 0.01 versus control), and great cardiac vein resistance increased from 4 +/- 21 to 15 +/- 19% (p less than 0.01 versus control). A similar significant response was observed for groups B1 and B2. Regional coronary vasoconstriction during adrenergic stimulation after combined drug therapy was only observed in patients with significant left anterior descending artery stenosis. These data suggest that in some patients with severe coronary artery disease, combined beta-adrenergic and calcium channel blockade modified regional coronary responses to adrenergic stimulation with an inhomogeneous distribution of blood flow to potentially ischemic regions without affecting total coronary blood flow. These data also imply that an improvement in anginal symptoms after combined drug therapy may be due primarily to mechanisms that reduce myocardial oxygen demand rather than to improved myocardial oxygen supply.

Regional coronary hemodynamic responses during the cold pressor test: lack of effect of nitroglycerin

The effects of large coronary vessel dilation on responses to immersion of a hand and forearm in ice water for 1 minute (that is, the cold pressor test) were calculated for 17 patients. Regional coronary blood flow and aortic and left ventricular pressures were continuously measured before and during two cold pressor tests, each performed before and after administration of sublingual (0.4 mg) or low dose intracoronary (0.01 mg) nitroglycerin. During the initial cold pressor test, heart rate and coronary pressures increased in all patients; total and regional coronary resistance usually increased in patients with severe coronary artery disease and usually decreased in patients with a normal coronary angiogram. Sublingual nitroglycerin induced important systemic effects, but intracoronary nitroglycerin did not; both induced dilation of coronary arteries viewed angiographically. Regardless of the route of nitroglycerin administration, coronary hemodynamic responses were directionally similar during the repeat cold pressor test compared with the initial one. These data support the concept that changes in tone of the large coronary arteries are not important in producing the cardiac responses observed during the cold pressor test.

Addition of nifedipine to maximal beta-blocker-nitrate therapy: effects on exercise capacity and global left ventricular performance at rest and during exercise

Nifedipine is a potent coronary vasodilator in the resting state and an effective afterload-reducing agent. This study was undertaken because of the concern that the addition of nifedipine to beta-blocker therapy could produce serious untoward hemodynamic consequences. Although this combination is usually well tolerated, occasional reports suggest that the combination of nifedipine and beta-blocking agents may increase the likelihood of congestive heart failure, severe hypotension or exacerbation of angina. Further, there is a need to know if the addition of nifedipine to therapy with maximally tolerated doses of long-acting nitrates and beta blockers would provide further symptomatic relief without excessive adverse effects. Finally, the effect of adjunctive nifedipine on global left ventricular performance at rest and during exercise was examined. Sixteen patients, all of whom had 3 or more episodes per week of angina pectoris despite therapy with long-acting nitrates and beta blockers, were selected. Radionuclide ventriculography was performed at rest and during exercise; global ejection fractions (EFs) were determined by manually tracing the left ventricular end-diastolic perimeter with an electronic cursor. In the first phase, beta blockers and nitrates were used; in the second phase nifedipine, 10 mg every 6 hours, was added and titrated to reduce systolic blood pressure at rest by at least 10 mm Hg or until intolerable adverse effects occurred. When nifedipine was added to therapy, the difference between global EF at rest and during exercise was reduced from - 0.15 to + 0.02 (p less than 0.00001); exercise duration was increased from 431 seconds to 532 (p less than 0.001), with only 8 patients limited by angina, compared with 16 during the initial therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Attenuation of coronary vascular resistance by selective alpha 1-adrenergic blockade in patients with coronary artery disease

Alpha-adrenergic-mediated coronary vasoconstriction during stress such as cold pressor testing may contribute to myocardial ischemia by increasing coronary vascular resistance in patients with severe coronary artery disease. Nonselective alpha-receptor blockade with phentolamine abolishes both the peripheral and coronary vasoconstriction during cold pressor testing, but causes reflex tachycardia and increased inotropy. To determine the role of selective alpha 1-receptor blockade, the changes in coronary vascular resistance during cold pressor testing were measured in 18 patients with coronary artery disease before and after intravenous administration of 100 mg of trimazosin. Cold pressor testing was performed at a constant paced subanginal heart rate of 95 +/- 5 beats/min (+/- 1 SD). Before trimazosin, cold pressor testing increased mean arterial pressure by 9 +/- 4% (102 +/- 14 to 111 +/- 14 mm Hg, p less than 0.001) with no change in coronary sinus blood flow, but significantly increased coronary vascular resistance by 15 +/- 19% (1.02 +/- 0.46 to 1.15 +/- 0.57 units, p less than 0.05). Five minutes after trimazosin, cold pressor testing increased mean arterial pressure by 6 +/- 5% (p less than 0.001) with a marked attenuation of the increase in coronary vascular resistance (6 +/- 11%, p = NS), which was significantly less than before trimazosin (p less than 0.02). Trimazosin did not increase plasma norepinephrine concentration at rest, suggesting that in the dosage used trimazosin caused selective alpha 1-receptor blockade.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemodynamic and coronary effects of molsidomine at basal state, during atrial pacing, and during cold pressor test in patients with stable angina pectoris

Heart rate (HR), cardiac output (CO), coronary sinus blood flow (CSF), left ventricular systolic pressure (LVSP), left ventricular end-diastolic pressure (LVEDP), mean arterial (MAP), and coronary arteriovenous difference for oxygen (AVDcO2) were measured in patients with stable angina pectoris without cardiac failure before and 40 to 60 minutes after administration of 2 or 3 mg of molsidomine. In 20 patients these measurements were made in basal state during spontaneous rhythm. In eight of these patients (including three receiving beta blockers) the measurements were made during atrial pacing. In eight other patients, all receiving long-term beta-blocker therapy, the measurements were made during cold pressor test. At the basal state in spontaneous rhythm, a gradual reduction in the LVSP to 70% or less of its initial value was observed in four patients receiving 3 mg of molsidomine (two of whom received beta-blocker treatment). The LVSP was immediately restored by vascular filling. In the 16 other patients molsidomine decreased LVSP, LVEDP, MAP, CO, and double product (DP = LVSP X HR). The AVDcO2 was unchanged. CSF and myocardial oxygen uptake index (MVO2 = CSF X AVDcO2) were decreased. During atrial pacing, hemodynamic and coronary effects were similar to those seen in the basal state. During the cold pressor test, the increases in LVSP, MAP, and LVEDP were significantly reduced by molsidomine. The variations in CSF and coronary resistance (MAP/CSF) were also significantly different after administration of molsidomine, with better metabolic regulation of the coronary circulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Dynamic coronary obstruction as a cause of angina pectoris: implications regarding therapy

The strong link demonstrated at autopsy between coronary atherosclerosis and angina pectoris led to the important concept that a fixed obstruction of 1 or more coronary arteries was the pathophysiologic cause of angina: myocardial ischemia and angina occurred when myocardial oxygen demand out-stripped the capacity of the diseased coronary artery to deliver oxygen. Therapeutic strategies were based on attempts to lower myocardial oxygen needs induced by physical and emotional stress. However, the finding that dynamic increases in coronary vascular resistance can also either precipitate ischemia or reduce the threshold of myocardial oxygen consumption (MVO2) at which it occurs has profoundly altered our understanding of the pathophysiologic features of angina and, therefore, its treatment. Dynamic coronary obstruction can occur at the large-vessel level, causing Prinzmetal's or variant angina. It is also possible that in some patients a continuum of large-vessel coronary vasoconstrictor tone exists, causing the common clinical situation manifested by angina with variable thresholds of onset. Recent studies have demonstrated that increases in the resistance offered to flow by small coronary arteries too small to be imaged by angiography can also decrease anginal threshold. The fact that ischemia can be precipitated by dynamic increases in large- or small-vessel coronary resistance has important implications for the therapy of angina pectoris. In those persons who mostly have a dynamic component contributing to their coronary obstruction, primary intervention with vasodilator therapy, including nitrates and calcium-channel blocking agents, are probably most effective therapeutically.(ABSTRACT TRUNCATED AT 250 WORDS)

Immediate and long-term effects of nicardipine, at rest and during exercise, in patients with coronary artery disease

Haemodynamic effects of nicardipine were studied in 12 patients with documented coronary artery disease. Following nicardipine 10 mg, given intravenously to patients at rest, the heart rate increased, mean arterial pressure decreased, cardiac index increased, and systemic vascular resistance decreased significantly. Compared with the control exercise values, significant increases in heart rate and cardiac index and significant decreases in mean arterial pressure, systemic vascular resistance, and left ventricular end diastolic pressure occurred when nicardipine, 10 mg i.v., was given to the patients during exercise. All 12 patients complained of angina during the exercise phase, but following treatment with nicardipine, 10 mg i.v., only four patients reported angina when exercising to the same level. Exercise capacity on oral nicardipine treatment tended to increase whilst the ejection fraction response to exercise did not change. Thus, nicardipine was a potent vasodilator, which produced a marked reduction of systemic vascular resistance and left ventricular end diastolic pressure during exercise.

Calcium channel blockers in emergency medicine

Diltiazem, nifedipine, and verapamil inhibit calcium entry into cells via different mechanisms with different pharmacologies. They display different relative effects on different cardiovascular functions, a complex interplay of direct actions and adrenergic reflexes. Peripheral arterial vasorelaxation causes adrenergic reflex activity which opposes their direct negative chronotropic, dromotropic, inotropic, and hypotensive actions. Verapamil's most potent activity is electrophysiologic, and nifedipine's effects are hemodynamic; diltiazem acts like a less-potent combination of verapamil and nifedipine. All three drugs are efficacious in angina. These three drugs may not be interchangeable in all patients, but individualization of therapy is possible. Future indications for calcium channel blocker therapy may include hypertrophic cardiomyopathy, cerebral vasospasm, migraine headaches, pulmonary hypertension, asthma, esophageal spasm, intestinal ischemia, Raynaud's phenomenon, dysmenorrhea, and premature labor.

Nifedipine-induced fingertip vasodilation in patients with Raynaud's phenomenon

The effect of nifedipine on fingertip hemodynamics was studied in 10 patients with Raynaud's phenomenon. Fingertip blood flow (FBF) was determined in a 20 degrees C environment by venous occlusion air plethysmography and fingertip vascular resistance (FVR) was calculated from the mean blood pressure and the FBF. Nifedipine, administered as a 10 mg sublingual dose, increased FBF in 8 of the 10 patients. FVR for the 10 patients decreased 40% from 40.7 +/- 10.8 to 24.2 +/- 6.1 U (p less than 0.05). Seven of the 10 patients were followed in a crossover placebo-controlled clinical trial. The frequency and severity of Raynaud's phenomenon was less in all seven patients when taking nifedipine as compared to placebo. Nifedipine-induced fingertip vasodilation may contribute to clinical improvement in some patients with Raynaud's phenomenon.

Effects of prostacyclin on coronary hemodynamics at rest and in response to cold pressor testing in patients with angina pectoris

To assess the effect of prostacyclin on the diseased coronary circulation basally and, in particular, on the coronary responses to the cold pressor test, a small dose of 4 ng/kg/min and a large dose of 8 to 10 ng/kg/min was infused in 11 patients with stable angina pectoris. Coronary blood flow was measured by coronary sinus thermodilution technique. The mean blood pressure decreased from 97 +/- 5 to 89 +/- 5 mm Hg during the low-dose infusion (p less than 0.005) and to 81 +/- 5 mm Hg during the high-dose infusion (p less than 0.001); the heart rate increased from 65 +/- 4 to 69 +/- 4 beats/min during the low-dose infusion (p less than 0.05) and to 78 +/- 5 beats/min during the high-dose infusion (p less than 0.001). Systemic vascular resistance decreased by 11 +/- 4% with small doses (p less than 0.05) and by 38 +/- 4% with large doses (p less than 0.001) of prostacyclin, and coronary vascular resistance decreased by 16 +/- 7% (p less than 0.05) with the small dose and by 29 +/- 6% (p less than 0.001) with the large dose of prostacyclin. Seven of 11 patients showed a baseline vasoconstrictor response to the cold pressor test (increase in coronary vascular resistance of 11 +/- 2%). This increase in coronary vascular resistance was not altered by either the small or the large dose of prostacyclin. Thus, prostacyclin causes marked coronary and systemic vasodilation, with no evidence of selective enhancement of the sensitivity of the diseased coronary circulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Temporal evolution of changes in left ventricular function induced by cold pressor stimulation. An assessment with radionuclide angiography and gold 195m

The evolutionary changes in left ventricular function induced by cold pressor stimulation were investigated at 90 second intervals by rapid sequential first pass radionuclide angiography using the short half life tracer gold 195m. The results in 12 subjects with normal coronary arteries were compared with those in 12 patients with coronary artery disease. Left ventricular ejection fraction fell significantly from resting values in both groups after 1 minute of cold pressor, but only in patients with coronary disease was the significant fall maintained at 2.5 and 4 minutes. In both groups, the maximum decrease in ejection fraction occurred after 1 minute, whereas the maximum rise in systolic blood pressure occurred after 2.5 minutes. New abnormalities of regional ventricular function developed in 10 normal subjects after 1 minute of cold, with a total of 12 new abnormal segments. Only two such segments were seen at the later stages of imaging. Twenty one new segments developed after 1 minute in the coronary disease group, and 13 segments remained abnormal after 4 minutes. Three patients, two of whom had left main stem stenoses, showed persistent abnormalities of ventricular function after 2 minutes of recovery from cold stimulation. Thus left ventricular function changes rapidly during a period of cold stimulation in both those without and those with coronary disease. When the cold pressor test is used with multiple gated equilibrium imaging, the timing of imaging may be crucial to the results and interpretation of the test. The discordance between functional changes and rise in blood pressure is further evidence that alterations in afterload are not solely responsible for cold induced abnormalities.