Exercise tolerance in patients with angina pectoris. Daily variation and effects of erythrityl tetranitrate, propranolol and alprenolol

Zibotentan in Microvascular Angina: A Randomized, Placebo-Controlled, Crossover Trial

BACKGROUND

Microvascular angina is associated with dysregulation of the endothelin system and impairments in myocardial blood flow, exercise capacity, and health-related quality of life. The G allele of the noncoding single nucleotide polymorphism RS9349379 enhances expression of the endothelin-1 gene (EDN1) in human vascular cells, potentially increasing circulating concentrations of Endothelin-1 (ET-1). Whether zibotentan, an oral ET-A receptor selective antagonist, is efficacious and safe for the treatment of microvascular angina is unknown.

METHODS

Patients with microvascular angina were enrolled in this double-blind, placebo-controlled, sequential crossover trial of zibotentan (10 mg daily for 12 weeks). The trial population was enriched to ensure a G allele frequency of 50% for the RS9349379 single nucleotide polymorphism. Participants and investigators were blinded to genotype. The primary outcome was treadmill exercise duration (seconds) using the Bruce protocol. The primary analysis estimated the mean within-participant difference in exercise duration after treatment with zibotentan versus placebo.

RESULTS

A total of 118 participants (mean±SD; years of age 63.5 [9.2]; 71 [60.2%] females; 25 [21.2%] with diabetes) were randomized. Among 103 participants with complete data, the mean exercise duration with zibotentan treatment compared with placebo was not different (between-treatment difference, -4.26 seconds [95% CI, -19.60 to 11.06] P=0.5871). Secondary outcomes showed no improvement with zibotentan. Zibotentan reduced blood pressure and increased plasma concentrations of ET-1. Adverse events were more common with zibotentan (60.2%) compared with placebo (14.4%; P<0.001).

CONCLUSIONS

Among patients with microvascular angina, short-term treatment with a relatively high dose (10 mg daily) of zibotentan was not beneficial. Target-related adverse effects were common.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT04097314.

Rationale and design of the Medical Research Council's Precision Medicine with Zibotentan in Microvascular Angina (PRIZE) trial

Microvascular angina is caused by cardiac small vessel disease, and dysregulation of the endothelin system is implicated. The minor G allele of the non-coding single nucleotide polymorphism (SNP) rs9349379 enhances expression of the endothelin 1 gene in human vascular cells, increasing circulating concentrations of ET-1. The prevalence of this allele is higher in patients with ischemic heart disease. Zibotentan is a potent, selective inhibitor of the ETA receptor. We have identified zibotentan as a potential disease-modifying therapy for patients with microvascular angina. METHODS: We will assess the efficacy and safety of adjunctive treatment with oral zibotentan (10 mg daily) in patients with microvascular angina and assess whether rs9349379 (minor G allele; population prevalence ~36%) acts as a theragnostic biomarker of the response to treatment with zibotentan. The PRIZE trial is a prospective, randomized, double-blind, placebo-controlled, sequential cross-over trial. The study population will be enriched to ensure a G-allele frequency of 50% for the rs9349379 SNP. The participants will receive a single-blind placebo run-in followed by treatment with either 10 mg of zibotentan daily for 12 weeks then placebo for 12 weeks, or vice versa, in random order. The primary outcome is treadmill exercise duration using the Bruce protocol. The primary analysis will assess the within-subject difference in exercise duration following treatment with zibotentan versus placebo. CONCLUSION: PRIZE invokes precision medicine in microvascular angina. Should our hypotheses be confirmed, this developmental trial will inform the rationale and design for undertaking a larger multicenter trial.

Diastolic perfusion time at ischemic threshold in patients with stress-induced ischemia

BACKGROUND

To evaluate the relevance of diastolic perfusion time on the mechanisms underlying stress-induced ischemia, 16 patients with coronary artery disease and seven patients with syndrome X underwent five randomized stress tests (upright and supine exercise with and without therapy, transesophageal atrial pacing).

METHODS AND RESULTS

Exercise duration Time to 0.1 mV ST segment depression, heart rate, rate-pressure product, and diastolic perfusion time were evaluated for each patient during stress tests. In both groups, variability coefficients of the above-mentioned parameters were not different at rest. At ischemic threshold (0.1 mV ST segment depression) in patients with coronary artery disease, the variability coefficient of exercise duration (40.1 +/- 22.2) was significantly higher (p less than 0.0001) than those of heart rate (12.8 +/- 2.9), rate-pressure product (14.8 +/- 3.3), and diastolic perfusion time (0.39 +/- 0.1). The variability coefficient of diastolic perfusion time was also significantly (p less than 0.0001) lower than those of heart rate and rate-pressure product. Similarly, the variability coefficient of diastolic perfusion time (0.44 +/- 0.1) in syndrome X patients was significantly lower (p less than 0.0001) than those of exercise duration (28.2 +/- 9.4), heart rate (12 +/- 1.4), and rate-pressure product (14.6 +/- 1.3).

CONCLUSIONS

Fixed diastolic perfusion time at ischemic threshold, despite different kinds of stress tests and variability of heart rate and rate-pressure product, indicates the relevant role of diastolic perfusion time in determining myocardial ischemia.

Effect of a bradycardic agent on the isolated blood-perfused canine heart

Bradycardic agents could limit the consequences of myocardial ischemia via two mechanisms: by decreasing myocardial oxygen demand (MVO2) and by increasing diastolic coronary blood flow (CBF). We investigated whether the benzazepinone UL-FS 49 affects only sinus node cells or also smooth muscle and/or myocardial cells. To avoid confounding interactions with the periphery, we performed experiments on 11 isolated, blood-perfused canine hearts. Injection of UL-FS 49 (1 mg/kg i.c.) significantly reduced heart rate (HR) from 104 +/- 7 to 93 +/- 7 min-1 (mean +/- SEM) and increased stroke volume (n = 6: 9.8 +/- 1.1 vs. 13.2 +/- 1.6 ml), so that cardiac output remained unchanged (n = 6: 1.1 +/- 0.1 vs. 1.2 +/- 0.1 l/min). The contractile state, assessed by isovolumic peak systolic pressure, was unaltered by UL-FS 49 (n = 5: 72 +/- 6 vs. 72 +/- 6 mmHg). At a constant coronary arterial pressure (CAP) of 80 mmHg, mean CBF was slightly decreased (102 +/- 11 vs. 97 +/- 10 ml/[min.100 g]) by UL-FS 49, such that mean coronary resistance remained unchanged (0.9 +/- 0.1 vs 1.0 +/- 0.1 mmHg.min.100 g/ml). The slight decreases in arteriovenous oxygen content difference (n = 6: 6.6 +/- 0.7 vs. 6.5 +/- 0.7 ml/100 ml) and in CBF lead to a calculated, significant decrease in MVO2 (n = 6: 6.9 +/- 0.5 vs. 6.0 +/- 0.4 ml.100 g/min). In conclusion, UL-FS 49 at the dose used decreases MVO2 by reducing HR in isolated canine hearts. In the absence of negative inotropic and vasodilating effects, cardiac output is maintained via increased stroke volume, and CAP will likely be preserved in situ. Thus, this specific bradycardic agent could be useful in treating ischemic myocardial disease.

Antianginal efficacy of exercise training: a comparison with beta blockade

Forty men with chronic stable angina and no prior myocardial infarction were studied. Exercise tolerance testing was carried out off treatment and after beta blockade. beta Blockers were stopped and the patients were randomised to a control group and a study group of patients who undertook a one year high intensity training programme. The groups were then restudied. Submaximum heart rate was reduced by 13 beats per minute by training and by 23 beats per minute by atenolol. Training increased the maximum heart rate by 10 beats per minute and atenolol reduced it by 29 beats per minute. The double produce ST threshold was increased from 183 to 205 by training but reduced to 143 by atenolol. Maximum ST depression was similarly reduced by both training and atenolol. As a result of the effects on maximum heart rate, training produced a greater improvement in exercise tolerance than atenolol with a treadmill time increased from 741 seconds to 1272 seconds with training compared with 974 seconds with atenolol. Other variables were similarly affected. Thus the antianginal efficacy of exercise training is as good as that achieved by beta blockade and represents an alternative to such treatment.

Abolition of exercise induced ST depression after exercise training and its recurrence after beta blockade

Exercise training can improve angina. A patient whose exercise tolerance test became normal after a year on an exercise programme nevertheless had a positive exercise test when he was taking a beta blocker. These results suggest that it may be undesirable to use beta blockers in patients with angina who are on exercise programmes.

Daily variations of ECG and left ventricular parameters at exercise in patients with anginal attacks but normal coronary arteriograms

In 21 patients with typical exercise-induced anginal pain but normal coronary arteriograms (group N) and in 14 patients with angiographically proved coronary stenosis (group C), symptom-limited ergometer exercise ECG and radionuclide angiocardiography were performed twice on two different days. Exercise-induced ST changes showed larger variations between the two exercise tests in group N than in group C ([delta ST1-delta ST2]: 0.07 +/- 0.06 mV in group N, 0.03 +/- 0.03 mV in group C, p less than 0.05). Rate pressure product and left ventricular ejection fraction at exercise also showed larger variations between the two tests in group N than in group C (p less than 0.001, p less than 0.05, respectively). However, substantial overlaps existed in some cases in the two groups. In conclusion, some of the patients with exercise-induced anginal pain but normal coronary arteriograms may have a variable threshold of exertional chest pain probably caused by variation in coronary vascular tone, and the other patients may have a fixed threshold of chest pain caused by other mechanisms.

Variability of results during repeat exercise stress testing in patients with stable angina pectoris: role of dynamic coronary flow reserve

In some patients with stable angina, the variability of results during repeated exercise tests is higher than in others with similar symptoms. The aim of the study was to assess whether this difference can be explained by a different susceptibility of the coronary arteries to vasoconstrictor stimuli. Ten patients (group A) with stable angina, who developed myocardial ischemia (angina and ST segment depression greater than 0.1 mV) following ergonovine-induced coronary constriction, and 10 other patients (group B) with stable angina, but a negative ergonovine test result, were subjected to two treadmill exercise tests. The variability of heart rate and heart rate-blood pressure product at 0.1 mV ST segment depression was significantly higher in group A than in group B (12 +/- 4 vs 4 +/- 4 bpm, respectively, p less than 0.001 and 3366 +/- 1900 vs 930 +/- 960 bpm X mm Hg, respectively, p less than 0.005), such as the variability of heart rate-blood pressure product at the onset of angina (3887 +/- 2400 vs 1428 +/- 1800 bpm X mm Hg, respectively, p less than 0.04). The remaining exercise parameters were always more variable in group A than in group B, but these differences did not achieve statistical significance. Thus patients with stable angina who develop myocardial ischemia in response to ergonovine have a larger variability of results during repeat exercise testing. Such findings could be explained by an enhanced susceptibility to the coronary constrictor effects of exercise resulting in dynamic changes in coronary flow reserve.

Acute haemodynamic effects of nifedipine at rest and during maximal exercise in patients with chronic cor pulmonale

The pulmonary hypertension of cor pulmonale can be reversed by sustained correction of hypoxia but continuous oxygen treatment poses problems in clinical practice. Alternative methods of relieving pulmonary vasoconstriction have therefore been explored. Eight patients with chronic cor pulmonale (five of them men) were studied to measure the haemodynamic effects of the calcium antagonist nifedipine, both at rest and on maximal, symptom limited exercise. The mean duration of exercise was unchanged by nifedipine (7.8 (SD 3.3) compared with 7.3(3.1) min). Cardiac output rose from 5.2(1.5) l min-1 to 8.6(3.3) 1 min-1 on exercise. Nifedipine increased resting cardiac output by 26%, but did not influence maximal exercise output. It did not significantly alter resting mean pulmonary artery pressure but reduced the level during exercise from 67(15) to 52(11) mm Hg. Nifedipine lowered resting pulmonary vascular resistance (PVR) by 32% and exercise PVR by 28%. It reduced supine mean systemic arterial pressure by 17%, standing pressure by 22%, and pressure at the maximal exercise level by 20%. Nifedipine lowered supine systemic vascular resistance (SVR) by 35%, standing SVR by 28%, and exercise SVR by 20%. Haemodynamic changes were achieved without adverse symptoms, alteration in arterial PO2, or impairment of calculated oxygen delivery. Nifedipine therefore reduced both pulmonary and systemic vasomotor tone at rest and during exercise. It did not alter exercise tolerance, which is probably limited by underlying respiratory disease. It seems possible therefore that nifedipine could delay the development of cor pulmonale, although this hypothesis remains to be tested.

Serial exercise testing in patients with effort angina: variable tolerance, fixed threshold

To investigate the frequency and mechanism of variable threshold angina, seven treadmill exercise tests were performed in each of 28 patients with stable effort angina and exercise-induced ST segment depression. Each patient had tests at 8 AM on 4 days within a 2 week period and on 1 of these days had three additional tests at 9 AM, 11 AM and 4 PM. Time to 1 mm ST depression increased from 277 +/- 172 seconds on day 1 to 319 +/- 186 seconds on day 2, 352 +/- 213 seconds on day 3 and 356 +/- 207 seconds on day 4 (p less than 0.05). Rate-pressure product at 1 mm ST depression remained constant. Similarly, time to 1 mm ST depression increased from 333 +/- 197 seconds at 8 AM to 371 +/- 201 seconds at 9 AM and to 401 +/- 207 seconds at 11 AM and decreased to 371 +/- 189 seconds at 4 PM (p less than 0.01). Again, rate-pressure product at 1 mm ST depression remained constant. The standard deviation for time to 1 mm ST depression, calculated as a percent of the mean for each patient's seven tests and then averaged for the entire group, was 22 +/- 11%. The standard deviation for rate-pressure product at 1 mm ST depression, calculated in the same way, was significantly less at 8.4 +/- 2.8% (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of beta-adrenergic blockade on the results of exercise testing related to the extent of coronary artery disease

Maximal treadmill testing was carried out in 50 patients with angiographically documented coronary artery disease (CAD) in the presence and absence of beta-adrenoceptor blockade. The results were related to the extent of CAD and interpreted relative to the clinical value of exercise testing. Maximal heart rate and systolic blood pressure were significantly lower during treatment with beta-blocking drugs. The average exercise duration was 1.3 +/- 1.9 minutes greater (+/- standard deviation), regardless of coronary anatomy. Of the 20 subjects with 3-vessel or left main CAD (severe CAD), 8 patients completed 3 stages (9 minutes) of exercise during treatment; only 4 did so without treatment. Angina was significantly more often the limiting symptom with severe CAD, and this association was abolished by beta blockade; 1 of 20 with severe CAD completed 3 stages of exercise and was not limited by angina without beta-blocking treatment, whereas 7 had these features during beta-blockade therapy. Maximal ST-segment depression was not related to the extent of CAD with or without therapy. Beta blockade suppressed the occurrence of ST depression, or delayed its appearance by an average of 2.0 +/- 2.3 minutes and reduced its severity by 0.5 +/- 0.9 mm. All tests in which ST depression was completely suppressed were associated with inadequate heart rate response, regarded as diagnostically inconclusive rather than negative. However, during beta-blocking treatment, 14 tests (28%) were inconclusive, which, in routine practice, would have necessitated repeat testing.(ABSTRACT TRUNCATED AT 250 WORDS)

A new oral slow release form of isosorbide dinitrate. Effect on the hemodynamics and exercise capacity of patients with angina

To assess the bioavailability of a new oral and slow release form of isosorbide dinitrate (ISDN-SR), we evaluated 12 patients with confirmed coronary artery disease, chronic stable angina pectoris and abnormal maximal exercise tests (angina-limited and associated with greater than or equal to 0.1 mV ST displacement). Each patient was known to have an increased exercise time after 0.4 mg of sublingual nitroglycerin. Patient responses to exercise on the treadmill at two, four, six, and eight hours after the double-blind administration of 40 mg of ISDN-SR were compared to an identical placebo. It is concluded that 40 mg of this slow release form of isosorbide dinitrate is bioavailable for at least eight hours as demonstrated by significantly improved exercise capacity of the majority (64 percent) of angina patients in this study, each of whom demonstrated anginal limitation to exercise and favorable responses to 0.4 mg of sublingual nitroglycerin.

The additive antianginal action of oral isosorbide dinitrate in patients receiving propranolol. Magnitude and duration of effect

Ten men with stable angina not completely relieved by full doses of propranolol (mean, 218 mg daily) were given double-blind, on alternate mornings, a placebo or an oral dose (5 to 30 mg) of isosorbide dinitrate (ISDN) previously titrated to lower sitting systolic blood pressure by 20 mm Hg. Patients had been trained in a protocol which precipitated angina after three to six minutes of bicycle exercise. On test days, with propranolol continued, bicycle exercise was performed until the appearance of angina before ISDN or placebo administration, and hourly thereafter for eight hours. Mean exercise duration was greater one hour after ISDN than after placebo by 182 sec (423 +/- 39 vs 241 +/- 13, p less than 0.001), and a difference of 63 sec was still present at six hours (p less than 0.002). At one hour, ISDN lowered resting systolic blood pressure by 26 mm Hg (from 114 +/- 5 mm Hg to 88 +/- 4 mm Hg; p less than .001) without appreciably changing heart rate. We conclude that ISDN is a very effective and reasonably long-acting antianginal supplement to propranolol.

Respiratory alkalemia during exercise reduces angina threshold

The effect of hyperventilation-induced alkalemia on angina threshold was evaluated in nine subjects who had a consistent pattern of chest pain and ST segment depression during exercise. For this study, the subjects performed graded bicycle exercise to angina during normal breathing and during hyperventilation. The maximum workload achieved was not significantly different between normal breathing and hyperventilation exercise. However, in five subjects who had arterial alkalemia during hyperventilation exercise (mean pH = 7.52), the heart rate X blood pressure product (HR X BP) at angina was 224 X 10(2) compared with 240 X 10(2) during normal breathing exercise (P less than 0.05). Four subjects appeared to hyperventilate, but were not alkalemic (mean pH = 7.40). Their HR X BP at angina was not significantly different between the two exercise periods (288 X 10(2) vs 284 X 10(2). In conclusion, the threshold for angina during exercise fell in the five patients in whom hyperventilation caused alkalemia. This finding suggests that the alkalemia interfered with myocardial oxygen supply.

Comparison of the results and reproducibility of arm and leg exercise tests in men with angina pectoris

The results and reproducibility of arm and leg exercise tests were compared in 11 men with angina pectoris induced by both forms of testing. Leg testing was performed using a bicycle ergometer; arm testing was performed using the same apparatus modified to permit arm cranking. Subjects performed 2 days of arm and 2 days of leg testing over a 2 week period. Four tests were performed on each test day. The duration of exercise, oxygen uptake, heart rate, systolic and diastolic blood pressures and the rate-pressure product were determined at the onset of angina. Within day and between product were determined at the onset of angina. Within day and between day coefficients of variation were low and similar for arm and leg tests, indicating that both forms of testing are highly reproducible. Performing four tests on a single day did little to reduce variability. Oxygen uptake increased between the first and second arm or leg test on a single day, but there was little change after the second test. Repetition of the arm and leg tests did not affect performance over the study period. It is concluded that the reproducibility of arm exercise testing in men with angina pectoris is comparable with that of leg exercise. Subjects with angina induced by arm exercise who cannot perform leg testing can be evaluated and followed up with arm exercise tests.

Cardiovascular responses to repeated treadmill exercise testing soon after myocardial infarction

To determine the response to repeated treadmill exercise testing soon after uncomplicated myocardial infarction, 24 males (mean age 54 +/- 6 years) performed two symptom-limited tests several days apart 3, 7 and 11 weeks after the acute event. Significant within-week differences were noted for peak exercise tolerance (mets) and peak heart rate at 7 weeks (p less than 0.05). Significant within-week differences in these variables were not noted for other weeks or for systolic blood pressure or heart rate-systolic blood pressure product for any of the three test periods. No significant within-week differences were noted for any variable recorded at a submaximal work load of 4 mets. The frequency of exercise-induced ischemic ST-segment depression, angina pectoris and premature ventricular complexes did not change from visit to visit and was highly reproducible (p less than 0.01). All test variables measured at peak exercise increased significantly between 3 and 11 weeks after infarction. We conclude that cardiovascular responses to symptom-limited exercise testing are highly reproducible in the 3 months after uncomplicated myocardial infarction. Changes in the response to treadmill exercise tests performed several weeks apart reflect alterations in cardiovascular performance.

Effect of beta-adrenergic suppression by propranolol on coronary collateral development in response to chronic coronary ischemia in dogs

Acute left circumflex coronary artery (LC) occlusion in conscious dogs caused marked ischemia in the myocardium supplied by the occluded artery, as judged by the radioactive microsphere technique for determining blood flow distribution. With the chest open, LC pressure distal to the occlusion fell to 21 +/- 1.9% of aortic pressure. By 8 weeks after gradual LC occlusion with an ameroid constrictor, collateral development had restored coronary blood flow distribution to near-normal under basal conditions and during pacing, at a heart rate of 200 beats/min. The only evidence for ischemia was in the subepicardium within the distribution of the unoccluded left anterior descending artery, which provided the extra collateral blood flow. Distal LC pressure was 70 +/- 1.7% of aortic pressure. Propranolol 160 mg orally every 6 hours for 8 weeks had no detectable effect on coronary collateral development, as judged by blood flow distribution or distal LC pressure. The only significant difference for the propranolol dogs was a slight transmural shift away from the subendocardium in the left anterior descending region.

Beta-adrenergic blockade in stress protection. Limited effect of metoprolol in psychological stress reaction

In a model system the influence of mental stress on blood pressure and heart rate was studied in normal persons and in patients with hypertension (WHO grade III). Metoprolol was employed to investigate the preventive effect of beta-adrenergic blockade on the response to stress. In all groups blood pressure increased significantly during mental stress. The effect was not inhibited by metoprolol. The rise in heart rate, however, was depressed by beta-blockade. Reaction time, opticomotor coordination and concentration ability were studied as parameters of vigilance, but no significant difference between the metoprolol and control groups were observed. Thus, metoprolol only influenced the heart rate in mental stress and it did not affect vigilance.

Exercise testing for detection of myocardial ischemia in patients with abnormal electrocardiograms at rest

This review consists of two parts: (1) discussion of the electrophysiologic mechanisms that are believed to produce ventricular repolarization changes during the electrocardiographic stress test, and (2) clinical assessment of the electrocardiographic changes with stress in patients with an abnormal electrocardiogram at rest. In the first part, the mechanisms of S-T segment elevation, S-T segment depression, T wave changes and linked S-T and T wave changes are reviewed. In the second part, all electrocardiographic abnormalities at rest are grouped into four categories: (1) changes that mask the manifestations of ischemia, (2) changes that stimulate or exaggerate the manifestations of ischemia, (3) changes that have no important effect on the manifestations of ischemia, and (4) changes that reproduce the patterns of acute myocardial infarction after an apparent healing. The reported studies of electrocardiographic stress testing in patients who have abnormal electrocardiogram at rest are summarized.

Medical therapy of angina pectoris

The pathophysiology of angina pectoris is best understood as an imbalance between oxygen supply and demand. The primary determinants of myocardial oxygen demand are heart rate, arterial pressure, heart size, myocardial contractility, and myocardial mass. The medical therapy of angina pectoris is directed toward reducing myocardial oxygen demand by reducing the workload of the heart and the specific determinants listed. The most common medications used in the treatment of angina pectoris are nitroglycerin and propranolol. Nitroglycerin reduces myocardial oxygen demand primarily by reducing heart size and arterial pressure. Propranolol reduces oxygen demand primarily by reducing heart rate. Medical therapy is generally effective in controlling the symptoms of angina pectoris in 80% or more of the patients and allows them to lead useful and productive lives.

Quantitative evaluation of vitamin E in the treatment of angina pectoris

Because of previous reports of the beneficial effect of vitamin E in angina pectoris patients, 48 patients, with both stable angina and positive (chest pain plus ishemic ST depression) maximal exercise treadmill tests, participated in a double-blind cross-over study of 6 months of vitamin E and 6 months of placebo therapy, separated by a 2 month no treatment period. All 48 patients had positive selective coronary arteriograms (75 per cent obstruction of at least a major coronary artery) and/or Q wave ECG evidence of previous myocardial infarction (Minnesota criteria). Evaluation of drug effectiveness was based on performance of serial maximal exercise treadmill tests, serial systolic time interval measurements, and daily angina diaries. No statistically significant differences between the two treatment studied. It is concluded that a large dose of vitamin E (1,600 I.U. of d-alpha-tocopherol succinate daily) for 6 months in patients with stable angina pectoris fails to increase the exercise capacity, improve left ventricular function, or reduce the frequency of chest pain.

Reproducibility of exercise tests in patients with symptomatic ischaemic heart disease

In 50 patients with ischaemic heart disease prospective analyses of the reproducibility of exercise tests at 3-month intervals were performed. The same method of testing was used repeatedly in a smaller group of patients 3 or more times at 6- to 8-week intervals. No significant differences were found in maximal heart rate, maximal systolic blood pressure, rate-pressure product, and total work. Symptoms resulting in the discontinuation of exercise were unchanged in 94 per cent of patients. The evaluation of the electrocardiographic recordings revealed good agreement in 94 per cent of patients. The evaluation of the electrocardiographic recordings revealed good agreement in ST segment depression and ST segment elevation. The reproducibility of arrhythmic events was very poor. The standardized electrocardiographic exercise test is, therefore, recommended for objective evaluation of various interventions in patients with manifest ischaemic heart disease, both in short-term and long-term follow-up studies.

Left ventricular wall motion response to intravenous propranolol

The effects of intravenous propranolol on left ventricular wall motion and hemodynamics were studied in 16 patients, 12 with significant coronary artery disease and four with chest pain but no coronary disease. Eight patients received 0.10 mg/kg and eight received 0.15 mg/kg of propranolol intravenously. All underwent atrial pacing at a constant rate. Left ventricular angiograms were performed before and 20 minutes after propranolol. At both doses, propranolol caused no significant change in left ventricular systolic or diastolic pressures, either before or immediately following ventriculography. Cardiac index fell significantly (3.4 plus or minus 0.2 [SEM] to 2.6 plus or minus 0.1 L/min/m-2) with the higher dose only. Of the ten patients with coronary artery disease and adequate ventriculograms, one patient had a normal left ventricle, two had regional hypokinesis, only three had areas of hypokinesis and akinesis, two had dyskinetic and akinetic areas, and two had areas of hypokinesis, akinesis and dyskinesis. No changes in regional contractility occurred with propranolol except for a minimal increase in hypokinesis in one patient at each dosage and equivocal development of a new area of slight hypokinesis in one patient and minimal apex of dyskinesis in another at the higher dosage. Of the four patients without coronary artery disease, two were affected by propranolol, one with initial regional akinesis and dyskinesis had slight worsening with propranolol and one with regional hypokinesis developed a definite new area of hypokinesis. Therefore, propranolol, even in large intravenous doses, resulted in no significant change in left ventricular wall motion in patients with coronary artery disease.

Exercise tolerance in patients with angina pectoris after pentaerythritol trinitrate and alprenolol studied by two different methods

Exercise tolerance has been studied by two different methods, heart-rate-controlled exercise and stepwise increased load, in 12 patients with angina pectoris. The response to a beta-adrenergic blocking agent, alprenolol, and an alkyl nitrate derivative, pentaerythritol trinitrate (PETRIN) was studied by the two methods after double-blind administration of the drugs. Rating scales were used to quantitate the degree of dyspnoea, angina pectoris and tiredness in the legs. After PETRIN both methods showed significant increases in exercise tolerance (19 and 21 per cent). The heart-rate-controlled test showed a significant increase (33%) after alprenolol, but the change was not significant by the other method. In the patients studied, heart-rate-controlled exercise discriminated between active drug and placebo better than the stepwise increased load test, what might have been due to more optimal matching of the loads obtained in the heart-rate-controlled test. Indications are given about how to design an exercise study in patients with angina pectoris.

Hemodynamic predictors of myocardial oxygen consumption during static and dynamic exercise

Hemodynamic predictors of myocardial oxygen consumption (MVO 2 ) during static and dynamic exercise were examined in ten normal subjects. Studies were done under the following circumstances: 1) during upright bicycle exercise at an average heart rate of 147 beats/min, 2) during static exercise with an isometric load in the left hand equal to 17% of the maximal voluntary contraction (MVC), and 3) during combined dynamic exercise (average heart rate 147 beats/min) and static exercise using 17% MVC of the left hand. Mean myocardial blood flow (MBF) was 181 ml/100 gm LV/min during dynamic exercise, 98 ml/100 gm LV/min during static exercise, and 201 ml/100 gm LV/min during combined static and dynamic exercise. Addition of a static load to the dynamic load resulted in a higher blood pressure (average 12 mm Hg), MVO 2 and MBF than during dynamic exercise alone. MVO 2 correlated best with products of heart rate and blood pressure regardless of whether the blood pressure was obtained by a central aortic catheter ( r = 0.88) or by a blood pressure cuff ( r = 0.85).

When the current data were combined with previous data, 82 determinations of MVO 2 and MBF in 29 normal subjects during several levels of upright exercise were available for analysis. Forty-four determinations were done during dynamic upright exercise, 18 during exercise after propranolol, ten during combined static and dynamic work, and ten during static work alone. MVO 2 correlated best with the product of heart rate and blood pressure ( r = 0.86). Heart rate alone correlated better with MVO 2 ( r = 0.82) than did the tension time index ( r = 0.65) or the product of systolic blood pressure, heart rate, and ejection time ( r = 0.68). The readily measured variables of heart rate and of heart rate x blood pressure correlated well with MVO 2 in normal young men during exercise under a wide variety of circumstances.

Sustained effects of nitroglycerin ointment in patients with angina pectoris

Cutaneous absorption of nitroglycerin is a well-documented phenomenon which may have unique advantages for the sustained prophylaxis of angina pectoris. Therefore, we have examined the effects of nitroglycerin ointment and placebo on exercise capacity in 14 patients with angina pectoris. Nitroglycerin ointment produced a significant increase in exercise capacity which persisted for at least three hours. Concomitant sustained changes in systolic blood pressure and resting heart rate were observed. Electrocardiographic evidence of myocardial ischemia was significantly reduced. Chronic administration in six patients did not reduce the effects of either nitroglycerin ointment or sublingual nitroglycerin. Nitroglycerin ointment appears to be a truly long-acting nitrate. While evidence of nitrate toxicity or tolerance was not observed in the present study, additional information is required before the widespread use of this agent can be recommended.

Effect of propranolol on myocardial oxygen consumption and its hemodynamic correlates during upright exercise

Measurements were made of heart rate, aortic blood pressure, systolic ejection period/beat, myocardial blood flow, and myocardial oxygen consumption in nine normal young men during three bouts of upright bicycle exercise: 1) at the workload which produced a heart rate of 120 beats/minute, 2) at the higher workload necessary to produce a heart rate of 120 beats/minute after administration of intravenous propranolol 0.25 mg/kg, and 3) with infusion of propranolol, at the same workload as the first exercise bout. Comparing exercises 1 and 2, we found a much higher workload was required to produce the same heart rate after propranolol. The blood pressure, heart rate-blood pressure product, and myocardial oxygen consumption were the same despite the much greater level of exertion. Comparing exercises 1 and 3, the heart rate, blood pressure, heart rate-blood pressure product, and myocardial oxygen consumption were all significantly lower during exercise 3 after propranolol despite the fact that the same degree of exercise was being done. As in previous studies, the heart rate-blood pressure product was an excellent correlate of myocardial oxygen consumption despite the change in contractility induced by propranolol. The systolic ejection period was prolonged significantly altering the tension-time index (TTI), which became an inadequate index of myocardial oxygen consumption. It is concluded that the heart rate-blood pressure product is a good index of myocardial metabolic needs during exercise and the relationship is undistorted by marked changes in contractility, but the tension-time index is a poor correlate. This data emphasizes the fact that the relative metabolic loads for the whole body and for the heart are determined separately and may not change in parallel with a given intervention.

Comparative evaluation of sublingual long-acting nitrates

Ten hospitalized patients performed two exercise tests per day on five consecutive days to determine the efficacy and duration of action of three sublingual long-acting nitrate preparations: isosorbide dinitrate, pentaerythritol trinitrate, and erythrityl tetranitrate. The duration of exercise to the point of ischemia, manifest as typical anginal pain and/or 1.0 mm ST-segment depression, was determined 45 min and 100 min after each long-acting nitrate was administered.

These results were compared with the duration of exercise after placebo and two minutes after nitroglycerin administration. The mean durations of exercise in two tests after placebo were 62.5 sec and 58.4 sec (not significant) and the mean durations of exercise after nitroglycerin administration were 90.5 sec and 88.4 sec, both different from placebo ( P < .001). There was no difference from placebo found 55 min after taking nitroglycerin. The mean durations of exercise 45 min after erythrityl tetranitrate, isosorbide dinitrate and pentaerythritol trinitrate were 89.1, 87.5, and 87.5 sec respectively and all were different from placebo ( P < .01). Mean durations of exercise 100 min after erythrityl tetranitrate, isosorbide dinitrate, and pentaerythritol trinitrate were 76.4, 75.5, and 69.7 sec and none were significantly different from placebo.

This study indicates that each long-acting nitrate is effective for at least 45 min and suggests that they should not be given on a fixed dosage schedule but rather should be taken prophylactically whenever an angina-provoking situation is anticipated.