A primary stenting strategy as an alternative to fibrinolytic therapy in acute myocardial infarction. An analysis of results in hospital and at 6 weeks and 6 months

OBJECTIVE

To report the feasibility and results to 6 months of a primary stenting strategy in patients with acute myocardial infarction (AMI).

DESIGN

Prospective, single-centre, observational study.

SETTING

A tertiary referral teaching hospital (Royal North Shore Hospital, Sydney), July 1997 to November 1998.

SUBJECTS

102 (of 194) consecutive patients presenting to the emergency department with AMI who were eligible for fibrinolytic therapy, and for a primary stenting strategy. The first 50 patients were under 70 years of age, and had not had previous coronary artery bypass grafting (CABG). The following 52 patients included patients up to 80 years and with previous CABG.

OUTCOME MEASURES

Major adverse cardiac and cerebrovascular events: death, reinfarction, cerebrovascular accident (CVA) and repeat target lesion revascularisation, in hospital, and at 6 weeks and 6 months. Minor in-hospital adverse events: bleeding requiring blood transfusion, vascular complications and new-onset heart failure. Time delays to treatment, and duration of hospital stay.

RESULTS

Normal flow was established in the infarct-related artery in 97/102 patients (95%). Stenting, percutaneous transluminal coronary angioplasty (PTCA), CABG or medical therapy was performed in 74, 11, 9 and 8 patients, respectively. Minor in-hospital events, time delays and hospital stay were similar to those reported previously. At 6 weeks, major adverse cardiac and cerebrovascular events had occurred in 5% of patients (four repeat target lesion revascularisation and one reinfarction). By 6 months, repeat target lesion revascularisation had been performed in an additional 10% of patients. No deaths had occurred.

CONCLUSIONS

A primary stenting strategy can be performed safely, without significant delays and with excellent short and intermediate term outcomes.

Biochemical markers of acute myocardial infarction: strategies for improving their clinical usefulness

We investigated the early diagnostic utility, including incremental value, of the serum cardiac markers creatine kinase (CK), CK-MB (mass and activity measurements), cardiac troponin T, and myoglobin in the diagnosis of acute myocardial infarction (AMI) in patients presenting to a major teaching hospital with chest pain and non-diagnostic electrocardiographs (ECG). The reference diagnosis of acute myocardial infarction was made by a single, independent cardiologist using World Health Organization criteria. CK and CK-MB mass were the only significant predictors of AMI at presentation to the Emergency Department. Logistic regression analysis revealed that CK did not significantly predict (P = 0.23) myocardial infarction once CK-MB mass was in the model. Using test results on follow up, in addition to presentation CK-MB mass, change in CK-MB mass was the only other significant independent predictor of AMI. Likelihood ratios for various levels of the significant markers in the logistic regression are given. In conclusion, CK-MB mass measurement was the only useful serum cardiac marker for the diagnosis of AMI in patients presenting with chest pain with non-diagnostic ECGs.

A randomized comparison of intravenous heparin with oral aspirin and dipyridamole 24 hours after recombinant tissue-type plasminogen activator for acute myocardial infarction. National Heart Foundation of Australia Coronary Thrombolysis Group

BACKGROUND

This study addressed the need for heparin administration to be continued for more than 24 hours after coronary thrombolysis with recombinant tissue-type plasminogen activator (rt-PA).

METHODS AND RESULTS

A total of 241 patients with acute myocardial infarction were treated with 100 mg rt-PA and a bolus of 5,000 units i.v. heparin followed by 1,000 units/hr i.v. heparin for 24 hours. At 24 hours, 202 patients were randomized to continue intravenous heparin therapy (n = 99) in full dosage or to discontinue heparin therapy and begin an oral antiplatelet regimen of aspirin (300 mg/day) and dipyridamole (300 mg/day) (n = 103). On prospective recording, there were no differences in the pattern of chest pain, reinfarction, or bleeding complications. Coronary angiography on cardiac catheterization at 7-10 days showed no differences in patency of the infarct-related artery. The proportion of patients with total occlusion (TIMI grade 0-1) of the infarct-related artery was 18.9% in the heparin group and 19.8% in the aspirin and dipyridamole group. In the patients with an incompletely occluded infarct-related artery, the lumen was reduced by 69 +/- 2% of normal in the heparin group and 67 +/- 2% in the aspirin and dipyridamole group. Left ventricular function assessed on cardiac catheterization and radionuclide study at day 2 and at 1 month showed no differences between the two groups. Left ventricular ejection fraction on radionuclide ventriculography at 1 month was 52.4 +/- 1.2% in the heparin group and 51.9 +/- 1.2% in the aspirin and dipyridamole group.

CONCLUSIONS

We conclude that heparin therapy can be discontinued 24 hours after rt-PA therapy and replaced with an oral antiplatelet regimen without any adverse effects on chest pain, reinfarction, coronary patency, or left ventricular function.

Determinants of recurrent ischaemia and revascularisation procedures after thrombolysis with recombinant tissue plasminogen activator in primary coronary occlusion

This paper reports the immediate effects of thrombolysis and their subsequent influence on revascularisation procedures and clinical outcome over the subsequent twelve months. Coronary arteriography was performed at 21 days on 131 of 145 patients who received recombinant tissue plasminogen activator (n = 68) or placebo (n = 63) within 2.5 hours of symptom onset after primary coronary occlusion. Patency rates (TIMI grades 2 and 3) of the infarct-related artery were 81% with plasminogen activator and 63% with placebo (P = 0.02). Early (within 21 days) angiography for recurrent ischaemia was necessary in 31 (21%) patients (20 plasminogen activator, 11 placebo NS) and definite reinfarction occurred in 8 (5%) patients (4 plasminogen activator, 4 placebo). During one year follow-up without planned secondary intervention, coronary artery bypass grafting was more frequent in patients who had received thrombolytic therapy (23% plasminogen activator, 4% placebo P = 0.001); coronary angioplasty procedures were similar in both groups (12% plasminogen activator, 11% placebo NS). Mortality at 21 days was 5% (4 plasminogen activator, 4 placebo) and at one year was 7% (5 plasminogen activator, 5 placebo). Logistic regression analysis identified models comprising characteristics predictive of subsequent bypass grafting (plasminogen activator, multivessel disease, occluded infarct-related artery) and coronary angioplasty (non-q wave infarction, severe (91-99%) residual stenosis, left anterior descending infarct-related artery). Initial non-q wave infarction was the only predictor of early recurrent ischemia (odds ratio 4, P = 0.02) irrespective of residual stenosis severity.

Short-term and long-term benefits of coronary angioplasty in unstable angina pectoris

Primary coronary angioplasty was attempted in 288 patients (206 men and 82 women) who presented with stable (50%) or unstable (50%) angina pectoris. The success rates of angioplasty and the subsequent revascularization requirements in these two angina categories were compared during a one year prospective follow-up. The site and distribution of coronary artery stenoses did not differ between the categories. Three hundred and five dilatations were attempted (149 in 144 patients with unstable angina and 156 in 144 patients with stable angina). Of these procedures, 265 (87%) were technically successful--133 (89%) in 128 patients with unstable angina and 132 (85%) in 120 patients with stable angina. Lower success rates were achieved in 29 attempted dilatations of vessels with chronic total occlusion (19 successful [66%], P = 0.002) and in 19 patients who presented with unstable angina after recent (within two weeks) infarction (10 patients with successful angioplasty, [53%], P less than 0.0001). Subsequent revascularization requirements after an initially successful angioplasty in 57 patients were greater in unstable (36 patients) than in stable angina (21 patients; P = 0.05) and reflected the greater frequency of repeat angioplasty in patients with unstable angina (22 patients) compared with those with stable angina (10 patients; P = 0.04) among patients with recurrent symptoms. At one year, 245 patients (85%)-121 treated for unstable angina and 124 treated for stable angina--experienced no angina during normal daily activities. We conclude that a primary angioplasty success rate of 89% can be achieved in patients with unstable angina pectoris but this rate is significantly lower in patients presenting after recent infarction. Repeat angioplasty for recurrent symptoms after a successful primary procedure is required more frequently in patients presenting with unstable angina.

Late (one month) reversible ischaemia after primary coronary occlusion treated with recombinant tissue plasminogen activator (rTPA)

The incidence of reversible ischaemia was assessed four weeks after primary coronary occlusion in 36 patients who had not required earlier revascularisation after randomisation to receive rTPA (n = 19) or placebo (n = 17). Coronary arteriography was performed at three weeks and thallium scintigraphy with dynamic stress testing at four weeks. Patients were followed for one year without planned intervention in the absence of symptoms. Managing physicians remained blinded to thrombolytic therapy. Patency rate of the infarct related artery at three weeks was greater after rTPA (rTPA 16, placebo 9; p = 0.04). Reversible perfusion defects within infarct related artery territory occurred with similar frequency in both treatment groups (rTPA 7, placebo 8). Multivessel disease was frequent (rTPA 11, placebo 12) but associated with a low incidence of reversible perfusion defects outside infarct related artery territory (rTPA 3, placebo 2). Thallium scintigraphy identified six of seven patients requiring subsequent revascularisation (sensitivity 86%, specificity 59%, negative predictive value 94%). Dynamic stress testing was positive for reversible ischaemia in 28% (rTPA 6, placebo 4) and identified two patients requiring revascularisation (sensitivity 29%, specificity 72%, negative predictive value 81%). The greater patency rate achieved with rTPA at three weeks after primary coronary occlusion was not associated with a significantly greater incidence of reversible perfusion defects at four weeks in patients who had not required prior revascularisation. The absence of reversible perfusion defects at four weeks was associated with a low incidence of revascularisation procedures during one year follow-up.

Comparison of the immediate and long-term effects of captopril and isosorbide dinitrate as adjunctive treatment in mild heart failure

1. The efficacy of captopril and isosorbide dinitrate (ISDN) as adjunctive therapy to digoxin and diuretics in mild heart failure was compared in a double-blind study. 2. Twenty-one patients were randomly allocated to captopril (twice or three times daily) or ISDN. Eighteen patients completed a protocol of placebo run-in, dose titration and maintenance treatment for 3 months. 3. Symptom-limited exercise tolerance, ejection fraction and radionuclide indices of diastolic function estimated by gated blood pool scan did not change with either treatment. 4. Captopril improved functional class (Canadian Cardiovascular Society) and reduced requirements for increased diuretic dosage at both 1 and 3 months of maintenance treatment. Patients treated with ISDN required increased diuretic and did not improve their functional class. Differences between the treatments were significant only for diuretic dosage requirements. 5. We conclude that adjunctive therapy of mild heart failure with captopril administered twice daily provides a diuretic-sparing effect and may improve functional class during 3 months of maintenance treatment.

Sympathetic (alpha-beta) or calcium channel blockade for hypertensive myocardial infarction? A haemodynamic comparison of labetalol and nifedipine

The haemodynamic impact of alpha- and beta-adrenoceptor blockade (labetalol) was compared with that of slow-calcium channel blockade (nifedipine) in 32 patients with sustained elevation of systemic arterial pressure (systolic blood pressure greater than 160; diastolic blood pressure greater than 95 mmHg) following a recent myocardial infarction (6-22 h). Patients with normal (pulmonary artery occluded pressure; (PAOP less than 18 mmHg; n = 16) or impaired (PAOP greater than 18 mmHg; n = 16) left ventricular function were randomized to labetalol (1 mg/kg i.v. 15 min) or nifedipine (20 mg sublingually) and haemodynamic profile was measured over 2 h. Both drugs equally reduced mean systemic arterial pressure (P less than 0.01 versus pretreatment control), and presumably left ventricular afterload; however, the heart rate (P less than 0.01) and cardiac index (P less than 0.01) increased after nifedipine, contrasting with reductions in both variables following labetalol (P less than 0.01). The elevated left ventricular filling pressure was reduced by both labetalol (P less than 0.05) and nifedipine (P less than 0.01) but the reduction was greater following nifedipine (-2 mmHg versus -5 mmHg, P less than 0.05). Thus both compounds were equally effective hypotensive agents. Labetalol consistently reduced cardiac stroke work and double product, important determinants of myocardial oxygen requirements; however, nifedipine afforded some improvement in cardiac performance in patients with left ventricular dysfunction.

A clinical model for predicting survival following acute myocardial infarction in patients without cardiogenic shock: a multivariate (Cox) analysis

A multivariate predictive model for early (six-month) survival based on Cox's proportional-hazards regression model was developed using data collected prospectively from 317 consecutive patients admitted with acute myocardial infarction to a coronary care unit (CCU). Of these, 63 (19.8%) died within the follow-up period. Patients with cardiogenic shock were excluded from the study. Variables associated with survival were sought from clinical, historical, electrocardiographic and radiographic variables recorded at the time of admission. On multivariate analysis, a stepwise selection procedure identified four variables which described the probability of survival for the six-month follow-up. These were: age, upper lung crepitations, marginal and also definite radiographic cardiomegaly on an anteroposterior radiograph. With this combination of clinical variables alone, using a survival probability partition value of 80%, the model had a sensitivity of 67% and a specificity of 75%. However, the model's predictive accuracy for death was 40%, compared to a predictive accuracy for survival of 90%. This clinical model is most useful for early discrimination of those patients at low risk of death within six months of CCU admission. Other predictive tests for premature death would need to exceed these discriminatory criteria to justify their cost and risks.

Haemodynamic dose-response effects of a transdermal nitrate delivery system in acute myocardial infarction with and without left heart failure

The haemodynamic effects of a transdermal nitroglycerin delivery system (NTG-TTS) were investigated in 67 patients with a recent myocardial infarction. The study objectives were to define the dose-response effects of NTG-TTS and to examine the influence of baseline haemodynamic status on subsequent response. Therefore, patients with normal cardiac function [pulmonary artery occluded pressure (PAOP) less than 18 mm Hg, n = 40] and those with acute heart failure (PAOP greater than 18 mm Hg, n = 27) were studied after one of three regimens (TTS-10, TTS-20, or TTS-40) with the intention of securing 10 evaluable patients in each group. In patients with acute heart failure, all three doses reduced the left ventricular filling pressure with a modest decrease in systemic arterial pressure; cardiac index and heart rate were unaltered. The systemic vascular resistance was significantly reduced from 120 min. In patients with normal left ventricular function, there were small but significant reductions in systemic arterial pressure and vascular resistance with limited increases in heart rate; the cardiac stroke work index was reduced. These results are compatible with actions of NTG-TTS mainly on capacitance vessels; PAOP fell with limited impact on systemic arterial pressure and vascular resistance index. This mode of nitrate delivery resulted in a low incidence of hypotension and side-effects; comparison with other delivery methods in myocardial infarction seems indicated.

Physical characteristics and clinical evaluation of a new disposable fibreoptic transducer-tipped catheter system

A new disposable fibreoptic transducer-tipped catheter manometer system was evaluated to assess its accuracy, stability of accuracy under prolonged simulated intra-arterial conditions, and dynamic characteristics. Maximum errors observed in the measurement of static pressure using a sample of five catheters (with one display unit) were 2 mmHg at 0 mmHg reference pressure, 2 at 20 mmHg, 4 at 40 mmHg, 4 at 100 mmHg and 9 at 200 mmHg. An immersion artifact caused a shift in baseline of up to 2 mmHg. Exposure of the transducer to 24 hours of simulated intra-arterial conditions (pulsatile pressure at 40 degrees C) resulted in errors of up to 7 mmHg for pressures up to 100 mmHg, and 11 mmHg for 200 mmHg, which were largely attributable to a drift in baseline pressure (up 6 mmHg by 24 hours). Consistent overestimation by the system suggested inappropriate gain setting within the display unit which, however, is not user-adjustable. The system exhibited uniform frequency response up to 33 Hz.

First-line treatment of left ventricular failure complicating acute myocardial infarction: a randomised evaluation of immediate effects of diuretic, venodilator, arteriodilator, and positive inotropic drugs on left ventricular function

A prospective randomised trial compared the immediate haemodynamic effects of intravenous diuretic (frusemide), venodilator (isosorbide dinitrate), arteriolar dilator (hydralazine), and positive inotropic stimulation (prenalterol) as first-line therapy for acute left ventricular (LV) failure following myocardial infarction. Forty-eight patients with transmural myocardial infarction and a pulmonary artery occluded pressure (PAOP) of greater than 20 mm Hg were studied within 18 h of admission to a coronary care unit. Both frusemide (-4 mm Hg; p less than 0.01) and isosorbide dinitrate (-6 mm Hg; p less than 0.01) reduced LV filling pressure without change in cardiac index and heart rate. Although both hydralazine and prenalterol increased cardiac index (p less than 0.01), the reduction in LV filling pressure (-2 mm Hg; p less than 0.05) was less than with frusemide and isosorbide dinitrate, and was associated with an increased heart rate (+8 and +13 beats min-1; p less than 0.01). These data suggest that in acute heart failure following myocardial infarction the four treatment modalities could be ranked in descending order of potential benefit as follows: venodilatation (isosorbide dinitrate)--decrease of LV pressure/work; diuretic therapy (frusemide)--decrease of LV pressure/work offset by a transient pressor effect; arteriolar dilatation (hydralazine)--decrease of LV pressure/work and of PAOP, but offset by tachycardia; and positive inotropic therapy (beta 1-agonist prenalterol)--tachycardia and augmented LV afterload. Combination of the former and latter agents, because of their differing modes of action, should offer haemodynamic advantages over monotherapy and deserves further evaluation.

Nifedipine following acute myocardial infarction--dependence of response on baseline haemodynamic status

The haemodynamic effects of nifedipine (20 mg sublingually) were studied in 40 patients with acute myocardial infarction within 18 h of the onset of symptoms. To determine the influence of preload and afterload on the haemodynamic response to nifedipine, patients were prospectively stratified equally into four groups of 10 patients based on systemic blood pressure level (less than or greater than 160/100 mm Hg) and level of left ventricular filling pressure [pulmonary artery-occluded pressure (PAOP) less than or greater than 18 mm Hg]. In all groups, nifedipine reduced systemic arterial pressure (p less than 0.01) and vascular resistance index (p less than 0.01); heart rate (p less than 0.01) and cardiac index (p less than 0.01) were increased. PAOP was reduced by nifedipine only in those hypertensive patients in whom it was initially raised; in these patients cardiac stroke volume index also increased (p less than 0.01). In hypertensive patients with normal PAOP the cardiac stroke work index was reduced. In patients with normal systemic and pulmonary arterial pressures, nifedipine had no beneficial effects on cardiac function. These data suggested that haemodynamic criteria may allow selection of patients for nifedipine therapy following myocardial infarction; clear advantages were evident only in hypertensive patients in both the presence and the absence of left ventricular failure.

The effects on left ventricular performance of verapamil and metoprolol singly and together in exercise-induced angina pectoris

Concurrent therapy with the calcium channel blocker, verapamil, and the beta-blocking group of compounds is usually felt to be clinically contraindicated due to the former's potent dromotropic and negative inotropic actions. The basis of this assumption was examined in a rest and exercise hemodynamic study of the effects of verapamil and the cardioselective beta-blocking drug, metoprolol, in 22 patients with stable angina pectoris and angiographically confirmed coronary artery disease. In a randomized study, 11 patients were assessed following intravenous verapamil (16 mg) alone, 11 following intravenous metoprolol (10 mg) alone, and all 22 were assessed on combination therapy. The plasma levels achieved at the time of each hemodynamic assessment were in the therapeutic range. At rest, verapamil alone significantly lowered systemic arterial pressure and vascular resistance; metoprolol alone lowered heart rate and increased systemic vascular resistance without change in systemic arterial pressure. Combination therapy reduced systemic arterial pressure and heart rate without change in cardiac output and systemic vascular resistance. During upright bicycle exercise, the changes were directionally similar. Depression of cardiac function (i.e., reduced cardiac output at increased pulmonary artery occluded pressure) occurred following metoprolol but not following verapamil; the addition of verapamil did not accentuate the depression of function induced by metoprolol. These results suggested that in patients with stable coronary artery disease, without manifest conduction system abnormality, the cardiac depressant actions of verapamil were countered by its vasodilator properties.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardioselective beta-blockade with atenolol and acebutolol following acute myocardial infarction: a multiple-dose haemodynamic comparison

In patients with acute myocardial infarction the haemodynamic relevance of the ancillary pharmacological properties of cardioselectivity and of intrinsic sympathomimetic activity (ISA) possessed by beta-blocking drugs is unclear. The dose-response effects of atenolol and acebutolol, two cardioselective compounds, the latter also possessing a degree of ISA, were therefore compared in a single-blind, dose-response, crossover study in patients within 18 h of suffering an uncomplicated acute myocardial infarction. The logarithmic cumulative dosage schedule achieved plasma concentrations in the clinical therapeutic ranges for both atenolol (0.05 +/- 0.04-0.19 +/- 0.03 micrograms/ml) and acebutolol (0.22 +/- 0.14-0.8 +/- 0.29 micrograms/ml). Incremental doses of intravenous atenolol (cumulative, 1-8 mg) resulted in significant decreases in systolic blood pressure, heart rate, cardiac output, stroke volume, and stroke work index (p less than 0.01 for each). Pulmonary artery occluded pressure (p less than 0.05) and systemic vascular resistance (p less than 0.01) increased. Incremental doses of intravenous acebutolol (cumulative, 10-80 mg) also resulted in significant decreases in systolic blood pressure, heart rate, cardiac output, stroke volume, and stroke work index (p less than 0.01 for each). Systemic vascular resistance increased (p less than 0.01); there was no consistent change in the pulmonary artery occluded pressure. Within the limits of the experimental protocol, the additional property of ISA possessed by acebutolol resulted in no statistically significant haemodynamic differences from atenolol. This may reflect either an insufficient degree of ISA possessed by acebutolol to confirm the original hypothesis, or its haemodynamic irrelevance in the presence of the increased sympathetic tone that is frequently present following acute myocardial infarction.

Haemodynamic dose-response effects of i.v. verapamil in coronary artery disease

As an aid to clinical therapeutic decisions, the haemodynamic dose-response effects following intravenous verapamil were evaluated in ten male patients with angiographically confirmed and stable coronary artery disease. Sitting at rest, following a control period with four i.v. boluses of saline, four equivalent boluses of verapamil (logarithmic cumulative dosage; 2, 4, 8 and 16 mg) were administered at four minute intervals; haemodynamic variables were recorded two to four minutes following each i.v. injection. The haemodynamic effects of the drug during upright bicycle exercise were evaluated by comparison of measurements made during a control steady-state exercise period with observations made at the same upright exercise workload (25 to 75 W) immediately following the maximum cumulative dose (16 mg). Following the four i.v. boluses, the plasma verapamil concentrations showed a log-linear increase (r = 0.82; p less than 0.001); the levels achieved (26 +/- 2 to 147 +/- 14 micrograms/l) were within the range at which substantial pharmacodynamic activity has been shown to be present. At rest, compared with control measurements after saline, these plasma concentrations of verapamil were associated with linear decreases in systemic vascular resistance (maximum delta SVR -720 dyne X s X cm-5/m2; p less than 0.01) and blood pressure (maximum delta MBP -8 mmHg; p less than 0.05) and linear increases in cardiac index (maximum delta CI +0.4 l/min/m2; p less than 0.05) and in pulmonary artery occluded pressure (maximum delta PAOP +3 mmHg; p less than 0.05). There was no significant trend of change in the heart rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Haemodynamic dose-response effects of i.v. nicardipine in coronary artery disease

The haemodynamic dose-response effects of the slow channel blocking agent nicardipine were evaluated in 10 male patients with angiographically confirmed coronary artery disease. At rest, following a similar control saline period, four doses of the drug (log cumulative dosage: 1.25, 2.5, 5.0 and 10.0 mg) were administered by i.v. infusion over a total duration of 40 min; haemodynamic variables were recorded in the 3-5 min following each 5 min infusion. During steady-state exercise the haemodynamic effects of the drug were evaluated by comparison of a control exercise period with observations made at the same workload (200-500 kpm) following the maximum cumulative dose (10 mg). Following the four i.v. infusions, the plasma nicardipine level increased log-linearly with the infused dose (r = 0.68). Compared with control measurements at rest after saline, these plasma concentrations (35 +/- 8 to 141 +/- 24 micrograms/l) resulted in a linear decrease in systemic blood pressure and vascular resistance with significant increase in cardiac index (maximum delta CI + 1.6 l min(-1) m(-2); P less than 0.01), stroke index (maximum delta SI + 11 ml/m2; P less than 0.01) and in pulmonary artery occluded pressure (maximum delta PAOP + 2 mm Hg; P less than 0.01). There was a significant increase in heart rate; the stroke work index was unchanged. During upright bicycle exercise the reduction in systemic blood pressure was accompanied by an increased exercise cardiac output without change in stroke index. The exercise pulmonary artery occluded pressure was unchanged compared with control observations, the stroke work index fell significantly (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Rest and exercise hemodynamic effects of sequential alpha-1-adrenoceptor (trimazosin) and beta-adrenoceptor (propranolol) antagonism in essential hypertension

The efficacy of acute beta blockade in essential hypertension is limited by reflex vasoconstriction. The aim of this study was to determine whether the latter response was modified by prior selective alpha-1-adrenoceptor blockade. A single-blind, within-patient, placebo-controlled evaluation of the immediate hemodynamic effects of sequential alpha-1 (trimazosin)- and beta (propranolol)-adrenoceptor blockade was undertaken in 10 men (34 to 58 years) with previously untreated essential hypertension. The study commenced with a 4-minute control period of constant-load (600 to 900 kpm/min) upright bicycle exercise, and measurements were made before (control) and 30 minutes after intravenous trimazosin (2 mg/kg) and exercise was then repeated; measurements at rest were again made 4 minutes after intravenous propranolol (0.2 mg/kg) before a final exercise period. Trimazosin at rest reduced systolic and diastolic arterial pressure and systemic vascular resistance without change in heart rate, cardiac output, or left ventricular (LV) filling pressure. During upright bicycle exercise the reductions in blood pressure were sustained without change in their rest-to-exercise increments. Other circulatory variables did not differ from control values. At rest the addition of propranolol further reduced systolic arterial pressure. Heart rate and cardiac output fell and systemic vascular resistance increased to its pretreatment control value. During exercise the changes at rest were sustained and the rest-to-exercise increments in blood pressure, heart rate, and cardiac output were reduced. LV filling pressure was significantly increased. In conclusion, alpha-1-adrenoceptor blockade modified the adverse effects of acute beta blockade at rest but not during exercise.

Hemodynamic trial of sequential treatment with diuretic, vasodilator, and positive inotropic drugs in left ventricular failure following acute myocardial infarction

The circulatory effects induced by two sequential intravenous treatment programs with a diuretic, arteriolar or venodilator , and a positive inotropic drug were studied in a randomized between-group trial in 20 male patients with radiographic and hemodynamic evidence of left ventricular (LV) failure following acute myocardial infarction (AMI). Furosemide induced a substantial diuresis in both groups of patients, in association with reductions in LV filling pressure (p less than 0.01) and cardiac output (p less than 0.05), without significant change in heart rate or systemic arterial pressure. The addition of isosorbide dinitrate was followed by reductions in the systemic arterial (p less than 0.01) and LV filling pressures (p less than 0.01) without significant change in the heart rate or cardiac output. Hydralazine after furosemide reduced systemic vascular resistance (p less than 0.01), but the fall in mean blood pressure (p less than 0.01) was limited by the increase in cardiac output (p less than 0.01); heart rate was also increased (p less than 0.01) and LV filling pressure fell (p less than 0.05). The final addition of the beta-1 adrenoceptor agonist, prenalterol, increased systemic arterial systolic pressure (p less than 0.05), cardiac output (p less than 0.05), and heart rate (p less than 0.01), and reduced systemic vascular resistance (p less than 0.01) in both groups; these changes were greatest in those pretreated with furosemide and isosorbide dinitrate. In both treatment pathways compared with control the reductions in systemic vascular resistance and left heart filling pressure were accompanied by increases in heart rate and cardiac output without substantial changes in systemic blood pressure. Which of these hemodynamic pathways offers the optimum prognosis awaits further study.

The effects on left ventricular performance of nifedipine and verapamil in exercise-induced angina pectoris

The differences between slow calcium blocking agents with respect to effects on heart rate, myocardial contractility and atrioventricular conducting time are well described; the relevance of such differences to the treatment of patients with impaired left ventricular function due to coronary heart disease is uncertain. The haemodynamic effects of equivalent hypotensive doses of nifedipine and verapamil were therefore compared in 20 patients with severe angina pectoris associated with angiographically documented coronary artery disease. The plasma concentrations of nifedipine (mean 57 +/- 19; range 27-77 ng/ml) and verapamil (mean 147 +/- 14; range 117-260 ng/ml) at the time of the haemodynamic measurements were of an order usually associated with substantial pharmacodynamic activity. Sitting at rest nifedipine resulted in reduction in systemic arterial pressure (P less than 0.05) and vascular resistance (P less than 0.01); both the heart rate (P less than 0.01) and cardiac output (P less than 0.05) increased without any significant change in the left heart filling pressure. In contrast, verapamil, which similarly reduced systemic blood pressure (P less than 0.05) and vascular resistance (P less than 0.01), increased cardiac output (P less than 0.05) and left heart filling pressure (P less than 0.05) without any change in heart rate. During upright bicycle exercise both drugs attenuated the angina induced in all subjects during the control exercise period. Despite reductions in systemic blood pressure and vascular resistance the cardiac output was unaltered on either drug at the same workload as in the control assessment. The reduction in exercise blood pressure following nifedipine induced a reflex tachycardia; this was not present, despite the similar hypotensive action, after verapamil.(ABSTRACT TRUNCATED AT 250 WORDS)

Enhanced haemodynamic effects of propranolol in acute myocardial infarction

To evaluate the possible influence of sympathetic activation on the haemodynamic response to intravenous beta-blockade, the dose-response characteristics of three boluses of propranolol were evaluated in 8 patients with uncomplicated infarction and compared in a similar number of patients with stable angina. Following a control period, when haemodynamic stability was confirmed, propranolol 2, 2 and 4 mg (cumulative dosage 2, 4 and 8 mg) was injected into the central circulation at 15 min intervals. Despite close matching in baseline control haemodynamic variables between the groups, in stable angina, propranolol resulted in dose-related depression of cardiac output without change in systemic blood pressure, whereas following myocardial infarction the drug induced significantly greater falls in cardiac output (P less than 0.05) and a dose-related decrease in systemic blood pressure. Despite the greater effects of propranolol on cardiac output following myocardial infarction, the left ventricular filling pressure was increased to a lesser extent compared with stable angina. The explanation for this observation may reside in a greater susceptibility of the left ventricular wall to increase its compliance, under conditions of high sympathetic stimulation, following beta-blockade. These data support experimental and biochemical evidence of sympathetic activation in myocardial infarction; the hyperadrenergic state conditions an augmented haemodynamic response to competitive antagonism of sympathetic stimulation at cardiac beta-adrenoceptors.

A randomised study of the haemodynamic changes induced by venodilatation and arteriolar dilatation singly and together in left ventricular failure complicating acute myocardial infarction

A randomised between-group study of the immediate haemodynamic effects of venodilatation by intravenous isosorbide dinitrate infusion (50-200 micrograms/kg/h) and arteriolar dilatation by intravenous hydralazine bolus (0.15 mg/kg) given either in random sequence (Groups 1 and 2; n = 12) or simultaneously (Group 3; n = 6) was undertaken in 18 men with radiographic and haemodynamic evidence (left ventricular [LV] filling pressure greater than 20 mm Hg) of LV failure 6-19 h following acute myocardial infarction. Control measurements (1 h) preceded either two consecutive 90-min treatment periods (Groups 1 and 2) or a single 90-min period (Group 3). Given independently, both drugs reduced systemic arterial pressure and vascular resistance, whereas only isosorbide dinitrate reduced LV filling pressure and only hydralazine increased cardiac output and stroke volume. Isosorbide dinitrate/hydralazine in combination significantly reduced LV filling pressure, systolic and diastolic arterial pressure, and total systemic vascular resistance. Cardiac output, stroke volume, and heart rate were increased. In conclusion, combined arteriolar dilatation and venodilatation appears to be of greater haemodynamic benefit than either alone, if the fall in mean systemic pressure does not compromise peripheral perfusion.

Comparison of haemodynamic dose-response effects of beta- and alpha-beta-blockade in acute myocardial infarction

The comparative haemodynamic dose-response effects of beta- (propranolol) or alpha- plus beta-blockade (labetalol) were evaluated in a randomised between-group study of 16 patients with an uncomplicated acute myocardial infarction. In equivalent beta-blocking doses both drugs equally reduced myocardial stroke work index and presumably myocardial oxygen requirements. However, although propranolol reduced heart rate and cardiac output, these haemodynamic changes were accompanied by an augmentation of systemic vascular resistance. In contrast, labetalol reduced heart rate, cardiac output without change in systemic vascular resistance. Moreover, concomitant alpha- and beta-blockade with labetalol resulted in lesser depression of cardiac output at equivalent beta-blocking doses to propranolol. These results suggest that the addition of alpha to beta-blockade may attenuate some of the adverse reflex circulatory consequences of pure beta-blockade; the usefulness of this pharmacological approach to the manipulation of the circulation in the early post-infarction period merits further study.

Hemodynamic effects of nifedipine during upright exercise in stable angina pectoris and either normal or severely impaired left ventricular function

The immediate effects of sublingual nifedipine (20 mg) were evaluated in 18 men with stable, exercise-related angina pectoris and angiographically confirmed coronary artery obstructions, stratified at the time of left ventricular (LV) angiography according to the degree of LV dysfunction supine at rest (Group 1: n = 9, left ventricular end-diastolic pressure [LVEDP] less than 20 mm Hg; Group 2: n = 9, LVEDP greater than 20 mm Hg). At rest, in the upright posture in both groups, nifedipine reduced the systemic vascular resistance (p less than 0.01). The systemic arterial mean (p less than 0.05) and diastolic (p less than 0.01) pressures were reduced despite an increase in the cardiac output (p less than 0.05). Heart rate was increased only in Group 1 (p less than 0.05). Pulmonary artery occluded pressure was unchanged in both groups. During upright bicycle exercise in all patients, compared to control measurements, systemic arterial pressure (p less than 0.01) and vascular resistance (p less than 0.05) were similarly reduced, while exercise cardiac output response and LV filling pressure did not change after nifedipine. Heart rate was increased in Group 1 (p less than 0.05) and decreased in Group 2 (p less than 0.05). Stroke volume during exercise after nifedipine decreased 1 ml/m2 in Group 1 (p greater than 0.05) and increased 2 ml/m2 in Group 2 (p greater than 0.05) compared to control measurements; the between-group difference in the exercise heart rate and stroke volume responses after nifedipine were significant at the 5% level.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative haemodynamic dose-response effects of intravenous propranolol, acebutolol and penbutolol in angina pectoris

The relevance of the ancillary pharmacological properties of intrinsic sympathomimetic activity (ISA) and cardioselectivity to the haemodynamic profile following intravenous beta-blockade was examined in a randomised study of propranolol (16 mg), acebutolol (160 mg) or penbutolol (4 mg) in 30 patients with stable angina pectoris. Haemodynamic measurements were undertaken at rest and during four minutes steady-state supine bicycle exercise (25 to 50 W), load limited to the angina threshold, before and after each drug. The randomised groups were statistically similar for major haemodynamic and clinical variables. The plasma concentrations achieved for each drug were in the therapeutic range. At rest, propranolol resulted in greater reductions in resting cardiac output and greater increase in pulmonary artery occluded pressure compared with acebutolol and penbutolol. During the sympathetic stimulus of dynamic exercise, penbutolol resulted in less depression of exercise cardiac performance than either acebutolol or propranolol. These observations are compatible with previous studies which suggested that the possession of ISA by a beta-blocking drug offset the depression of cardiac performance following intravenous beta-blockade; the benefits of ISA on haemodynamic profile appeared maximum at rest and were reduced or abolished during dynamic exercise.

The effect on left ventricular performance of nifedipine and metoprolol singly and together in exercise-induced angina pectoris

Clinical concern still exists regarding the potentially deleterious results of the combined negative inotropic effects of cardiac beta-adrenoceptor and slow calcium channel blockade in patients with impaired left ventricular function due to coronary heart disease. The haemodynamic effects of sublingual nifedipine (20 mg) and intravenous metoprolol (10 mg) singly and in combination were therefore studied in 20 patients with severe angina pectoris associated with angiographically documented coronary artery disease. The plasma concentrations of each drug at the time of the haemodynamic measurements were within the range associated with relief of exercise-induced anginal pain. Sitting at rest, nifedipine was associated with reductions in systemic arterial pressure (P less than 0.05), systemic vascular resistance (P less than 0.001), and increases in heart rate (P less than 0.01) and cardiac output (P less than 0.05) without significant change in the left heart filling pressure. In contrast, sitting at rest, metoprolol was associated with reductions in systemic blood pressure (P less than 0.05), heart rate (P less than 0.001) and cardiac output (P less than 0.05) and an increase in left heart filling pressure (P less than 0.01). After both drugs, similar directional changes were observed during upright bicycle exercise compared to the control exercise measurements. In combination, the negative inotropic effects of metoprolol were largely offset by the reduction of the systemic vascular resistance due to nifedipine. Conversely the reflex tachycardia following nifedipine was countered by metoprolol. Thus the combination reduced two of the major determinants of left ventricular oxygen consumption, namely heart rate and systemic blood pressure, at the expense of a small increase in left heart filling pressure. This may have explained the subjective improvement in anginal symptoms noticed by the majority of the patients. The combination of nifedipine and metoprolol was haemodynamically more advantageous both at rest and during exercise than either drug alone in our patients with depressed left ventricular function due to the coronary heart disease.

Is the intrinsic sympathomimetic activity (ISA) of beta-blocking compounds relevant in acute myocardial infarction?

The relevance of the intrinsic sympathomimetic activity (ISA) of beta-blocking compounds to the clinical therapeutics of acute myocardial infarction was evaluated in 20 patients with an uncomplicated acute myocardial infarction by comparing the haemodynamic effects of equivalent beta-blocking doses of propranolol (non-cardioselective; no ISA) and pindolol (non-cardioselective; 50% ISA). Consecutive eligible male patients admitted to a Coronary Care Unit were randomised following a 1 h control period to two separate studies. In Study 1 the short-term dose-response effects of propranolol (1-8 mg) or pindolol (0.1-0.8 mg) were assessed. In Study 2 comparison of the effects of single i.v. propranolol (8 mg) and pindolol (0.8 mg) doses was undertaken over 6 h. Haemodynamic variables and thermodilution cardiac output were subsequently recorded to compare the effects of each drug on the circulation. The plasma concentrations of propranolol and pindolol were in the recognised therapeutic range. Both drugs were clinically well-tolerated, the changes induced in haemodynamic variables following each drug demonstrated effective beta-blockade. Within the limits of the experimental protocol, these data did not suggest definite haemodynamic advantage for ISA of pindolol in acute myocardial infarction. These findings are perhaps due to sympathetic activation in acute myocardial infarction attenuating the haemodynamic impact of ISA.

Haemodynamic effects of selective alpha 1-blockade (trimazosin) in essential hypertension

As a preliminary to a larger clinical trial, the haemodynamic effects of the selective alpha 1-adrenoceptor antagonist trimazosin were studied at rest and during bicycle exercise in the upright position in 14 patients with uncomplicated, stable essential hypertension. Rest and exercise studies before the drug was given revealed no evidence of left ventricular pumping deficiency. A single intravenous bolus of trimazosin (2 mg/kg) resulted in a plasma concentration of 13.1 +/- 1.0 mg/ml 30 min after injection. This plasma concentration of trimazosin was associated with a reduction in the systemic vascular resistance (p less than 0.01); in the absence of any increase in the cardiac output, this resulted in a fall in the systemic blood pressure (p less than 0.01) at rest. Heart rate and left heart filling pressure were unchanged. During 4 min of upright dynamic exercise after drug, the increment in systemic blood pressure was similar to that in the control study; i.e., the absolute level of pressure was reduced (p less than 0.01). The increases in heart rate, cardiac output, and left heart filling pressure during exercise were also unchanged after drug compared with those measured in the control study. The left heart filling pressure and cardiac output were slower to increase at the onset of exercise after trimazosin, which may imply a degree of venodilatation. There were no hypotensive symptoms or large falls in blood pressure after trimazosin at rest, but following 4 min of submaximal upright bicycle exercise, three of the 14 patients developed postural hypotension.(ABSTRACT TRUNCATED AT 250 WORDS)

Haemodynamic dose-response effects of i.v. penbutolol in angina pectoris

The haemodynamic dose-response effects of intravenous penbutolol, a newer beta-adrenoceptor antagonist with intrinsic sympathomimetic activity but without cardioselectivity, were evaluated in 10 patients with angiographically documented coronary artery disease. Following four logarithmetically cumulative i.v. boluses (0.5-4 mg dosage range) there was a log linear increase in plasma penbutolol concentration; the levels achieved (51 +/- 8 to 219 +/- 19 ng/ml) were in the therapeutic range (12 to 250 ng/ml). Penbutolol resulted in a linear decrease in heart rate (maximum delta HR - 4 beats/min; P less than 0.01); there was a small increase in pulmonary artery occluded pressure which reached its maximum at the lower doses (maximum delta PAOP + 1 mm Hg; P less than 0.01). The resting cardiac output, blood pressure and calculated systemic vascular resistance were unchanged. During 4 min steady-state supine bicycle exercise there was attenuation of exercise cardiac output (delta C.I. - 0.6 1 min-1 m-2; P less than 0.01) and systolic pressor response (delta SBP - 13 mm Hg; P less than 0.01) compared with control observations without change in other measured or derived variables. The haemodynamic profile of penbutolol compared favourably with other beta-adrenoceptor antagonists previously evaluated under similar conditions in patients with ischaemic heart disease. Over the i.v. dose-range evaluated penbutolol attenuated exercise-induced angina with a relatively modest depression of cardiac performance; the small change induced in resting haemodynamic variables may, in part, have been contributed to by the intrinsic sympathomimetic activity of penbutolol.

Hemodynamic comparison of primary venous or arteriolar dilatation and the subsequent effect of furosemide in left ventricular failure after acute myocardial infarction

The hemodynamic effect of venous dilatation (intravenous isosorbide dinitrate [ISDN]) and arteriolar dilatation (intravenous hydralazine), both as firstline treatment and then combined with intravenous furosemide, were evaluated in a randomized, between-group comparison in 20 men with severe acute left-sided cardiac failure after myocardial infarction (MI). Both ISDN (50 to 200 micrograms/kg/hour) (Group 1) and hydralazine (0.15 mg/kg) (Group 2) reduced systemic arterial pressure (p less than 0.05) and vascular resistance (p less than 0.05). Pulmonary artery occluded pressure was reduced (p less than 0.01) only by ISDN, whereas heart rate (p less than 0.01), cardiac output (p less than 0.01) and stroke volume (p less than 0.05) were increased only after hydralazine. After ISDN, furosemide (1 mg/kg) decreased left-sided cardiac filling pressure by 1 mm Hg (p greater than 0.05), whereas after hydralazine, furosemide in a similar dose reduced pulmonary artery occluded pressure by 5 mm Hg (p less than 0.01). In both groups of patients, furosemide transiently increased systemic arterial pressure (p less than 0.05). Cardiac output was reduced (p less than 0.05) and systemic vascular resistance increased (p less than 0.05) in Group 1 patients after furosemide. Similar changes in both variables in Group 2 patients did not attain statistical significance. In conclusion, ISDN-induced venous dilatation is preferable to primary arteriolar dilatation by hydralazine as first-line treatment in acute left-sided cardiac failure. However, hydralazine and furosemide in combination were equally effective in reducing pulmonary artery occluded pressure and increasing cardiac output. The influences of each regimen on prognosis await further investigation.

Haemodynamic effects of frusemide and its influence on repetitive rapid volume loading in acute myocardial infarction

The haemodynamic effects of intravenous frusemide (1 mg/kg) were studied in 22 male patients with left ventricular failure following acute myocardial infarction. Radiographic pulmonary oedema was present in all patients and their average left heart filling pressure was 20 mmHg. Bolus injection of the drug was followed by immediate increases in systemic arterial pressure (P less than 0.05) and heart rate (less than 0.05); these declined to pre-injection values after 60 min. Following frusemide there were progressive reductions in left heart filling pressure (P less than 0.01), thermodilution cardiac output (P less than 0.01) and stroke volume (P less than 0.05) and a progressive increase in the derived systemic vascular resistance (P less than 0.05). There was an average diuresis of 860 ml during the 90 min following the frusemide injection. The influence of frusemide on left ventricular performance was studied by comparing the circulatory effects of passive leg raising in the control period with those at 30, 60 and 90 min after the drug. In the control period this manoeuvre increased left heart filling pressure, but not heart rate, cardiac output, stroke volume or systemic vascular resistance. Ninety minutes after frusemide, but not before, passive leg raising resulted in a significant increase in cardiac output (P less than 0.01) and stroke volume at a similar increment in filling pressure and a significant reduction in the systemic vascular resistance (P less than 0.05). These circulatory actions of intravenous frusemide are compatible with initial arteriolar constriction and venodilatation followed by depletion of blood volume with subsequent change in left ventricular pumping performance.

Comparative haemodynamic dose-response effects of intravenous propranolol and pindolol in patients with coronary heart disease

To determine whether the depression of left ventricular pumping activity associated with beta-blockade alone could be offset by a substantial degree of partial agonist activity, the haemodynamic dose-response effects of intravenous propranolol and pindolol were compared in a randomised between-group saline controlled study in twenty patients with angiographically proven coronary artery disease. The intravenous doses of propranolol (2-16 mg) and pindolol (0.2-1.6 mg) used were selected on the basis of published reports of equivalence in terms of exercise blockade of chronotropic beta-adrenoceptors. Following four intravenous boluses of each drug, administered according to a cumulative log-dosage schedule, there was a log-linear increase in the plasma concentrations of each drug. The range of plasma concentrations achieved were those which have been shown to be associated with substantial attenuation of sympathetic stimulation of cardiac beta-adrenoceptors. At rest propranolol resulted in dose-related linear reductions in heart rate and cardiac output and linear increases in left heart filling pressure and systemic vascular resistance compared with saline-controlled measurements. The only statistically significant change at rest after pindolol was a small increase in the left heart filling pressure. The calculated systemic vascular resistance was increased after propranolol but unchanged after pindolol. During supine bicycle exercise the systolic blood pressure increased less after propranolol than after saline or pindolol. The increments in all other measured haemodynamic variables during exercise were equally influenced by the two drugs.(ABSTRACT TRUNCATED AT 250 WORDS)

Arteriolar or venous dilatation in left ventricular failure following acute myocardial infarction: a haemodynamic trial of hydralazine and isosorbide dinitrate

We undertook a randomised between-group comparison of the haemodynamic effects of arteriolar dilatation and venodilatation in 20 males, following acute myocardial infarction, with persisting left ventricular failure after pretreatment with intravenous frusemide. All had radiographic pulmonary oedema and a pulmonary artery occluded pressure (PAOP) exceeding 15 mm Hg. The average cardiothoracic ratio was 52% (range 48-65%). Following control haemodynamic measurements, 10 patients received intravenous hydralazine (0.15 mg/kg) and 10 received intravenous isosorbide dinitrate infusion (50-200 micrograms/kg/h). Subsequent measurements were made at 30, 60, and 90 min. Isosorbide dinitrate reduced the PAOP by 3 mm Hg (p less than 0.01) and the mean systemic arterial pressure by 9 mm Hg (p less than 0.05) without significant change in the heart rate, cardiac output, or systemic vascular resistance. In contrast, hydralazine reduced the PAOP and systemic arterial pressure by a similar amount, but this was accompanied by a reduction in the systemic vascular resistance (p less than 0.01) and an increase in the cardiac output (p less than 0.01), heart rate (p less than 0.01), and stroke volume (p less than 0.01). This randomised study defines the contrasting haemodynamic results of arteriolar dilatation and venodilation in patients with resistant left ventricular failure following acute myocardial infarction. The different pharmacodynamic effects of these two methods of circulatory manipulation suggest that they are not mutually exclusive and together may offer therapeutic advantages.

Haemodynamic advantages of isosorbide dinitrate over frusemide in acute heart-failure following myocardial infarction

The immediate haemodynamic effects of intravenous frusemide (1 mg/kg) and intravenous isosorbide dinitrate (50-200 micrograms/kg/h) were compared in a prospective, randomised, between-group study in 28 men with radiographic and haemodynamic evidence of left ventricular failure following acute myocardial infarction. The diuresis induced by frusemide reduced the left heart filling pressure and cardiac output and transiently raised systemic blood-pressure. In contrast, isosorbide dinitrate was accompanied by a reduction in systemic blood-pressure and peripheral resistance with the result that the cardiac output was not decreased despite a large fall in the pulmonary vascular and left heart filling pressures. These results indicate that reduction of excessive preload by venodilatation may be haemodynamically superior to that induced by diuresis in terms of both reducing myocardial oxygen consumption and maintaining peripheral perfusion. The influence of these contrasting treatments on the prognosis of these high-risk patients warrants further study.

alpha- and beta-blockade with labetalol in acute myocardial infarction

On the hypothesis that the addition of alpha-blockade would mitigate the haemodynamic disadvantages of beta-blockade alone in the early stages of uncomplicated acute myocardial infarction, 15 patients were studied during the intravenous infusion of labetalol (0.5 mg/kg/h). The mean systemic arterial pressure was reduced by an average of 15 mm Hg. In the nine patients haemodynamically evaluated, the cardiac output (thermal dilution) was reduced without change in the heart rate or left heart filling pressure (pulmonary artery occluded pressure); left ventricular stroke work was significantly decreased. The reduction in these major determinants of myocardial oxygen consumption suggests that the combination of alpha- and beta-blockade may be haemodynamically advantageous in normotensive patients in the early stages of uncomplicated acute myocardial infarction.

Comparative haemodynamic dose response effects of propranolol and labetalol in coronary heart disease

The immediate haemodynamic dose response effects of beta blockade (propranolol: 2 to 16 mg) were compared with those of combined alpha beta blockade (labetalol: 10 to 80 mg) in a randomised study of 20 patients with stable angina pectoris. After control measurements, the circulatory changes induced by four logarithmically cumulative intravenous boluses of each drug in equivalent beta blocking doses were evaluated at rest, after which comparison of the effects of the maximum cumulative dose of each was undertaken during a four minute period of supine bicycle exercise. Propranolol, at rest, induced significant dose related reductions in heart rate and cardiac output, with reciprocal increases in the systemic vascular resistance and pulmonary artery occluded pressure; systemic arterial pressure was unchanged. Labetalol was followed by significant dose related decreases in systemic blood pressure and vascular resistance associated with a significant increase in cardiac output; heart rate and pulmonary artery occluded pressure were unchanged. The slope of the left ventricular pumping function curve relating output to filling pressure from rest to exercise was significantly depressed by propranolol but unchanged after labetalol. The less deleterious effects on left ventricular haemodynamic performance after alpha beta blockade in contrast to beta blockade alone in ischaemic heart disease may be attributable to the concomitant reduction in left ventricular afterload associated with the alpha blocking activity of labetalol.

Circulatory dose-response effects of hydrochlorothiazide at rest and during dynamic exercise in essential hypertension

The immediate and sustained circulatory effects of hydrochlorothiazide were evaluated at rest and during dynamic exercise in 24 patients with essential hypertension. Twenty-four hours after the first dose (50mg) there was a reduction in the resting systolic blood pressure, with attenuation of exercise tachycardia. During sustained therapy at two dose levels (50mg and 100mg), each of one month's duration, the systolic and diastolic blood pressure were reduced, both at rest and during dynamic exercise, without substantial difference between the two doses. Exercise tachycardia was attenuated during longterm treatment, without alteration of the pressor responses to exercise. The reduction in exercise tachycardia at the same workload in this study suggests that thiazides, in addition to their diuretic action, have a vascular component that augments the fall in systemic vascular resistance during dynamic exercise.

The antiarrhythmic effect of intravenous disopyramide in an open study

The antiarrhythmic effect of intravenous disopyramide phosphate was assessed in a multicentre open study of 141 patients admitted to coronary care units. Disopyramide was administered in a bolus dose of 2 mg/kg over 10 min with an optional second bolus of 1 mg/kg and infusion of 0.4 mg/kg hour. Atrial fibrillation was terminated in 57% of 56 patients, supraventricular tachycardia in 82% of 11 patients, ventricular tachycardia in 88% of 17 patients and premature ventricular contractions were controlled in 85% of 55 patients. Atrial flutter was terminated in only 2 of 17 patients (12%). Side effects occurred in 38% of the patients, the most frequent being those relating to anticholinergic properties of the drug (15%) or systemic hypotension (13%). Occasionally worsening of the arrhythmia (4%), QRS widening (3) or apparent hypertension (2%) were noted. It was concluded that intravenous disopyramide is an effective antiarrhythmic agent in the coronary care unit setting, but that side effects require close monitoring of dosage.

Haemodynamic advantages of combined alpha-blockade and beta-blockade over beta-blockade alone in patients with coronary heart disease

The acute haemodynamic effects of beta-blockade with propranolol and combined alpha-blockade and beta-blockade with labetalol were compared in a randomised study in 12 patients with coronary artery disease proved by angiography. Propranolol induced significantly greater depression of left ventricular function both at rest and during exercise than labetalol. This difference was probably attributable to the vasodilator activity of labetalol and the associated reduction in afterload offsetting the haemodynamic disadvantages of blockade of cardiac beta-adrenoceptors alone. The haemodynamic advantages of combined alpha-blockade and beta-blockade over beta-blockade alone may thus have therapeutic implications for the use of these treatments in patients with coronary heart disease.

Haemodynamic effects of sustained treatment with prazosin and metoprolol, alone and in combination, in borderline hypertensive heart failure

The sustained haemodynamic effects of prazosin (20-30 mg) and metoprolol (400-800 mg) alone and combined (half-dose) were evaluated in five patients with hypertension, left ventricular hypertrophy, and radiological cardiac enlargement. Measurements were made at rest and during isometric handgrip exercise. Blood pressure at rest was equally well controlled on each regimen. The heart rate and cardiac output (thermodilution) were reduced by metoprolol, even when combined with prazosin. Systolic ejection time was prolonged by metoprolol, but there were no changes in left ventricular dimensions at rest. During isometric handgrip the pressure increments were similar on each of the three regimens, although absolute diastolic pressure was lower on combined therapy. The arterial pressure increment on prazosin therapy was predominantly due to a rapid rise in heart rate and cardiac output, whereas with metoprolol and combined therapy the major contribution to the response was by peripheral vasoconstriction. Moreover, with the latter regimens there was a rapid rise in pulmonary artery occluded pressure, which did not occur with prazosin therapy. In conclusion, metoprolol alone, or combined with prazosin, caused significant depression of cardiac function, which was apparent only when the patients were subjected to the haemodynamic stress of isometric exercise.

Combined pre- and after-load reduction in hypertensive patients with cardiomegaly and normal filling pressure

1. Twelve hypertensive patients with cardiomegaly were treated with equivalent antihypertensive doses of prazosin (11 weeks) and β-adrenoceptor-blocking drug (9 weeks) in random crossover fashion.

2. At the end of each treatment period haemodynamic assessment included the response to isometric handgrip exercise (4 min at 30% of maximum voluntary contraction).

3. Resting cardiac index and heart rate were higher on prasozin although the latter was only 65 beats/min. Systemic vascular resistance and left ventricular filling pressure were insignificantly higher on β-adrenoceptor-blocking drug.

4. During isometric handgrip the blood pressure rise was similar on the two regimens, but the mechanism whereby it was achieved was quite different. On prazosin an increase in cardiac output accounted for the pressor response with virtually no change in systemic vascular resistance, whereas on β blockade there was a flat cardiac output response with a marked increase in the systemic vascular resistance.

5. Ventricular function curves indicated a predominant utilization of the Frank-Starling mechanism during β blockade, whereas enhanced contractility played a major role during prazosin treatment.

6. The isometric exercise response pattern during prazosin treatment resembles that in normal subjects whereas in the β blockade phase it corresponded to that in untreated hypertensive patients with left ventricular hypertrophy or cardiomegaly or to that in congestive heart failure patients.

7. There was no evidence of harmful effects of combined pre- and after-load reduction in hypertensive patients with cardiomegaly and normal filling pressure, even under conditions of moderately severe cardiac loading with isometric exercise.