Intravenous flecainide versus amiodarone for recent-onset atrial fibrillation

In a randomized, double-blind, controlled study of 98 patients with atrial fibrillation (AF) (present for > or = 30 minutes, < or = 72 hours, and a ventricular response of > or = 100 beats/min), intravenous flecainide (2 mg/kg, maximum 150 mg) was compared with intravenous amiodarone (7 mg/kg) and placebo. Exclusion criteria included significant left ventricular dysfunction, inotrope dependence, recent antiarrhythmic therapy, hypokalemia, and pacemaker dependence. Reversion to stable sinus rhythm within 2 hours of starting medication was considered likely to be due to drug effect. Twenty of 34 patients (59%) given flecainide, 11 of 32 (34%) given amiodarone, and 7 of 32 (22%) given placebo reverted to stable sinus rhythm in < or = 2 hours after starting medication (chi-square 9.87, p = 0.007). More patients reverted to stable rhythm with flecainide than with placebo (p = 0.005; odds ratio 5.1, 95% confidence interval 1.54 to 17.5). There was no significant difference between amiodarone and placebo or between flecainide and amiodarone. However, after 8 hours there were no significant differences in reversion between the treatment groups: flecainide (n = 23, 68%), amiodarone (n = 19, 59%), and placebo (n = 18, 56%). Amiodarone promptly reduced the ventricular rate, and this effect was maintained for 8 hours in those whose reversion to stable sinus rhythm was unsuccessful: flecainide was no more effective than placebo in controlling ventricular rate. Adverse effects were not significantly different in the 3 groups. Thus, intravenous flecainide results in earlier reversion of AF than does intravenous amiodarone or placebo. Amiodarone, although less effective in reverting AF, slows the rapid ventricular response.(ABSTRACT TRUNCATED AT 250 WORDS)

Placebo-controlled trial of enteric coated aspirin in coronary bypass graft patients. Effect on graft patency

OBJECTIVE

To determine whether slow-release enteric coated aspirin (100 mg daily), commenced before operation, improves the patency of saphenous vein (SV) coronary artery bypass grafts at six months.

DESIGN AND SETTING

Double-blind, randomised, placebo-controlled study at a teaching hospital.

RESULTS

One hundred and forty patients were randomly allocated to receive enteric coated aspirin or matching placebo. Similar groups of 50 (aspirin) and 52 (placebo) subjects completed the six months follow-up and had an angiogram to assess patency. Five patients treated with aspirin and nine who received placebo had at least one occluded SV graft; the distal ends of 6 of 128 SV grafts in aspirin-treated patients (4.7%) and 13 of 145 SV grafts in patients in the placebo group (9.0%) were occluded--the difference was not significant. An arterial graft was occluded in one other patient in each group (3% of arterial grafts). There was more postoperative blood loss, on average, in patients treated with aspirin, but the difference was not significant. Only one patient was withdrawn from long-term therapy because of possible gastrointestinal symptoms; most withdrawals from the trial were necessitated by commencement of aspirin or non-steroidal anti-inflammatory therapy for musculo-skeletal disorders.

CONCLUSIONS

The coronary bypass graft occlusion rate six months after surgery was low, and was lower on average in aspirin treated subjects but not significantly so. Long-term treatment with low-dose aspirin is recommended unless contraindicated.

Usefulness of atrial electrograms recorded via central venous catheters in the diagnosis of complex cardiac arrhythmias

OBJECTIVE

To assess the role of intravascular atrial electrograms in improving the diagnosis of complex cardiac arrhythmias in critically ill patients.

DESIGN

Prospective, clinical study comparing the accuracy of cardiac rhythm diagnosis using standard surface electrocardiogram (EKG) and intravascular atrial electrograms.

SETTING

Intensive care unit of a university teaching hospital.

PATIENTS

A total of 57 critically ill patients (44 cardiothoracic surgery, five acute myocardial infarction, two septic shock, six miscellaneous) with 85 complex cardiac arrhythmias that were unable to be diagnosed with certainty using the surface EKG.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The intravascular atrial electrogram altered diagnosis based on the surface EKG in 11 (13%) patients and confirmed rhythm diagnosis in 60 (71%) of 85 patients with arrhythmia. Of 61 patients with wide complex tachycardia, 40 (66%) were diagnosed as ventricular tachycardia (atrioventricular dissociation demonstrated on the atrial electrogram), and 11 (18%) as supraventricular tachycardia with aberrant conduction. Ten (16%) wide complex tachycardias could not be diagnosed with confidence using both surface EKG and intravascular electrogram. There were no adverse effects with this technique.

CONCLUSIONS

Intravascular atrial electrograms recorded via central venous catheters are useful in the diagnosis of complex cardiac arrhythmias, particularly ventricular tachycardia. The technique is safe, simple, and quick.

Effect of alpha 1-adrenoceptor blockade on ventricular ectopic beats inacute myocardial infarction

Experimental studies have shown that alpha1-adrenoceptor blockade can reduce ventricular arrhythmia associated with myocardial ischaemia. To examine the efficacy of prazosin in clinical acute infarction 38 patients were randomized, on presentation, to prazosin or placebo. Oral therapy was commenced at 0.5 mg, incremented and continued for seven days, Holter recordings being obtained for the first 48 hours and on day 7. The final dose of prazosin was 2.5 +/- 1.7 (SD) mg and placebo, 3.1 +/- 2.0 mg. During dose titration in the first 24 hours, and on day 7, there was no difference in ventricular ectopic beats. In the second 24 hours, ventricular ectopic beats averaged two per hour in the prazosin group (n = 9) and 60 per hour in placebo (n = 15) (P = 0.05, Mann-Whitney rank testing). The results indicate that alpha1-adrenoceptor blockade may reduce ventricular arrhythmia in clinical acute myocardial infarction. While early and adequate therapy is currently limited by vasodilation, this small study suggests that more extensive clinical trials will be warranted as relatively cardio-selective alpha1-adrenoceptor blocking drugs are developed.

Safety and convenience of a mechanical injector pump for coronary angiography

Coronary angiography and left ventriculography was performed in 5,887 consecutive patients over a 5-year period using a mechanical injector pump activated by a foot switch. Five coronary dissections occurred, four of the right coronary artery and one of the left internal mammary artery, which had been grafted to the left anterior descending artery. One patient had angina following an air embolus; there were no significant intramyocardial injections of contrast agent. The pressure generated in the catheter by hand injection of contrast agent was compared with that generated by the injector pump. Contrast agent was injected through a 7F Judkins Right 4 and an 8F Sones catheter by hand at slow, medium, and fast rates by hand and by the injector pump at 2,3, and 4 ml/sec; maximum pressure generated was recorded. Although the pressures generated through a Sones catheter were similar using both methods, pressures with hand injection were much more variable. The pressures generated with hand injection through a Judkins catheter were lower than those with pump injection, but again the pressures showed much greater variability with hand injection. The pump was found to be safe, reliable, predictable, and convenient when used for coronary angiography with Sones and Judkins catheters. It eliminates the need for a trained assistant during the procedure of coronary angiography.

Verapamil withdrawal as a possible cause of myocardial infarction in a hypertensive woman with a normal coronary angiogram

Verapamil is an effective and relatively-safe antihypertensive drug. Serious adverse effects are uncommon and mainly have been related to the depression of cardiac contractility and conduction, especially when the drug is combined with beta-blocking agents. We report a case in which myocardial infarction coincided with the introduction of captopril and the withdrawal of verapamil in a previously asymptomatic woman with severe hypertension. Possible mechanisms that involve a verapamil-related increase in platelet and/or vascular alpha 2-adrenoreceptor affinity for catecholamines are discussed.

Effectiveness of amiodarone on ventricular arrhythmias during and after acute myocardial infarction

A randomized, placebo-controlled study examined the effect of amiodarone on the incidence of ventricular arrhythmias after acute myocardial infarction (AMI). Two hundred patients with AMI were randomized to receive amiodarone, 200 mg every 8 hours for 1 month, followed by 200 mg/day, or placebo, starting 48 hours after the onset of chest pain. Twenty-four-hour Holter monitoring was performed on day 1, repeated after 8 days and subsequently at 3-month intervals. One hundred seventy-two patients were followed for 6 to 42 months and monitor data were available at 6 to 9 months in 129 patients. Amiodarone was well tolerated, with no serious side effects; 12 patients were withdrawn from therapy. At 6 to 9 months more than 1 ventricular premature complex per hour was present in 3 of the 59 amiodarone-treated patients (5%) and 24 of the 70 placebo-treated patients (34%) (p less than 0.02). Complex arrhythmias (multifocal, early cycle, repetitive, bigeminy, trigeminy or ventricular tachycardia) were present in 5 of 59 of the amiodarone-treated patients (8%) and 20 of 70 placebo-treated patients (28%) (p less than 0.005). Sixteen patients in the amiodarone group and 11 in the placebo group died (difference not significant). Thus, amiodarone can reduce the frequency and complexity of ventricular arrhythmias after AMI, but it is unlikely that this will result in a substantial beneficial effect on post-AMI mortality risk.

Comparison of pulsed Doppler and thermodilution methods for measuring cardiac output in critically ill patients

We obtained 145 consecutive cardiac output measurements in 38 critically ill patients, using the invasive thermodilution and the noninvasive pulsed Doppler methods. The mean thermodilution cardiac output (TDCO) was 5.7 +/- 1.87 L/min and the mean pulsed Doppler cardiac output (PDCO) was 5.16 +/- 1.66 L/min. The mean difference between the two measurements was 0.51 L/min with an SD greater than 1.6 L/min, reflecting the scattering of results. The overall correlation coefficient was .58. The intercepts were large and the regression equation some way from the line of equal values (TDCO = 2.28 + 0.66 PDCO). When the results were analyzed according to diagnosis or by group experience, there were some differences in the bias of the estimate; however, the SD of the difference between methods was greater than one liter/min in all groups. Thus, the pulsed Doppler method failed to estimate accurately TDCO in critically ill patients.

Comparison of transthoracic electrical impedance and thermodilution methods for measuring cardiac output

Cardiac output was measured 120 times in 27 critically ill patients using the thermodilution and transthoracic electrical impedance methods. Both the minimum and mean values for the distance between the inner electrodes, and a variety of values for the resistivity of blood (rho) were substituted in the Kubicek's empiric formula for calculating cardiac output by transthoracic electrical impedance. Using the mean distance between the inner electrodes and a rho-value of 150 ohm X cm gave the best agreement between the methods (mean difference 0.17 +/- 2.4 L/min). Ventilation alone or with positive end-expiratory pressure did not significantly affect the bias of the estimate, but both affected its precision when compared with measurements in spontaneously breathing patients (SD of mean difference 2.4 and 3.2 L/min, respectively, vs. 1.5 L/min). The pulmonary artery wedge pressure was significantly higher in patients with an abnormal diastolic impedance waveform (zero-wave), but there was no relationship between wedge pressure and base impedance per unit length between the measuring electrodes.

Cigarette smoking and ventricular arrhythmia in coronary heart disease

With use of 24-hour ambulatory electrocardiographic monitoring, the effect of 1 hour of cigarette smoking on cardiac rhythm in 73 patients with coronary heart disease was studied. Fifteen subjects had no arrhythmia; 37 subjects had fewer than 2 atrial or ventricular premature complexes (APCs or VPCs)/hour, with APCs possibly related to smoking in 2 and VPCs related to smoking in 1. Nineteen subjects had more than 2 VPCs/hour (range 4 to 368) and had 16 +/- 29 VPCs/hour (+/- standard deviation) less during than before smoking (p less than 0.05), associated with an increase in heart rate of 4.6 +/- 6.8 beats/min (p less than 0.01). In none of the 9 subjects with unifocal VPCs did multiform beats develop during or after smoking, whereas 3 of 10 subjects with multiform VPCs had only unifocal beats during and immediately after smoking. In 1 of these 19 subjects, frequent APCs developed during smoking. One other subject had frequent APCs unaffected by smoking and another had sinoatrial block, which disappeared during smoking on 1 of 3 monitorings. In conclusion, no sustained or high-grade ventricular arrhythmia was provoked by smoking; although APCs may have been related to smoking in a few persons, the frequency and complexity of VPCs tended to be reduced in these subjects with coronary artery disease.

Randomized controlled trial of vasodilator therapy after myocardial infarction

Hemodynamic changes and mortality and morbidity were compared in a randomized controlled trial of sodium nitroprusside after acute myocardial infarction. Fifty patients with a mean pulmonary capillary wedge pressure of more than 20 mm Hg within 24 hours of acute infarction were randomly assigned to one of two groups: 25 patients treated with nitroprusside and 25 treated with furosemide. Nitroprusside rapidly produced a sustained decrease in systemic vascular resistance and increase in cardiac index (thermodilution). After 1 hour the cardiac index had increased 16 +/- 3 (mean +/- standard error of the mean) percent (p less than 0.001) compared with a decrease of 7 +/- 3 percent with administration of furosemide (p less than 0.01). Differences in systemic vascular resistance and cardiac index in the two groups persisted throughout the 48 hour treatment period (p less than 0.001). Pulmonary capillary wedge pressure decreased rapidly with nitroprusside and slowly with furosemide so that, although it was significantly lower in the former group overall (p less than 0.001), by 48 hours the values were not different. Although beneficial acute hemodynamic effects of nitroprusside were demonstrated, there was no difference in mortality or in morbidity assessed clinically, by chest X-ray film, echocardiogram or graded treadmill stress testing after 6 months or 1 year.

Prazosin in the treatment of severe chronic congestive cardiac failure

The acute haemodynamic effects of prazosin 5 mg were investigated in 11 patients with severe chronic congestive cardiac failure. Six patients had their antifailure therapy discontinued while five continued on their usual medication. Two patients were exercised before and after prozosin. Following the drug, pulmonary capilary wedge pressure diminished 7 +/- 2(SE) mmHg (P < 0.005) and cardiac index increased 17 +/- 6% (P < 0.02). Mean arterial pressure fell in all subjects (- 9 +/- 2 mmHg; P < 0.001) and systemic vascular resistance was reduced in all but one (- 19 +/- 5%; P < 0.005). There was no significant change in heart rate. Four of the five subjects whose regular medications were continued were evaluated by clinical examination, chest X-ray, echocardiogram and treadmill stress test, before and after four weeks of prazosin therapy, one subject having died in this time. Two improved, one deteriorated and one remained unchanged. Thus, chronic prazosin therapy benefited individual patients but did not consistently provide long term improvement.

Comparison of vasodilator drug prazosin with digoxin in aortic regurgitation

Intravenous administration of the vasodilator sodium nitroprusside has beneficial haemodynamic effects in subjects with severe aortic regurgitation while acute digitalisation can produce unwanted effects associated with an increase in systemic vascular resistance. This study compares the haemodynamic effects of the vasodilator prazosin and digoxin in eight patients with isolated severe aortic regurgitation. Prazosin 5 mg orally resulted in a 12 +/- 3 (SE) per cent increase in cardiac index (thermodilution), maintained over four to six hours, while digoxin 0.75 mg intravenously did not change the cardiac index. Prazosin reduced mean arterial pressure by 9 +/- 3 mmHg and systemic vascular resistance by 18 +/- 4 per cent while digoxin resulted in a 6 +/- 2 per cent increase in the latter. Mean pulmonary capillary wedge pressure fell 3 mmHg with prazosin. In this group of patients with severe aortic regurgitation but without severe cardiac failure, the changes with either drug, studied in doses conventionally used, were small but those with prazosin were directionally more desirable than those resulting from digoxin.