Karl D. Donovan

Intravenous flecainide versus Amiedarone fof 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)

Transesophageal echocardiography in critically ill patients.

ObjectiveTo evaluate the safety and utility of transesophageal echocardiography performed by intensive care physicians in critically ill patients. DesignRetrospective chart review. SettingA 24-bed multidisciplinary adult intensive care unit in a 692-bed tertiary referral teaching hospital. PatientsTwo hundred fifty-five intensive care patients. InterventionsWe studied 255 consecutive intensive care patients who underwent transesophageal echocardiography between January 1996 and January 2000. Measurements and Main ResultsThree hundred eight transesophageal echocardiography studies were successfully performed; the probe could not be passed in one patient with a cervical fracture. The indications included unexplained hypotension (40%), known or suspected endocarditis (27%), assessment of ventricular function (15%), pulmonary edema (5%), source of embolus (4%), assessment of aorta (4%), and other (5%). In 67% of hypotensive patients, transesophageal echocardiography revealed the cause of hemodynamic instability, leading to a management change and improvement in blood pressure in 31%. This included surgery in 22% without the need for additional tests. Overall, transesophageal echocardiography findings led to a significant change in management in 32% of all studies performed. One patient receiving continuous positive airways pressure suffered pulmonary aspiration during tracheal intubation before transesophageal echocardiography, two patients had hypotension associated with sedative medication, and there was one case of oropharyngeal bleeding after probe insertion. ConclusionTransesophageal echocardiography when performed by intensive care physicians is a safe procedure and provides useful information for the evaluation and management of 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 (p) were substituted in the Kubiceks empiric formula for calculating cardiac output by transthoracic electrical impedance. Using the mean distance between the inner electrodes and a p-value of 150 ohmċcm 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.

Efficacy of flecainide for the reversion of acute onset atrial fibrillation

The efficacy and safety of intravenous flecainide to convert recent-onset atrial fibrillation (AF) (present for greater than or equal to 30 minutes and less than or equal to 72 hours and a ventricular response greater than or equal to 120 beats/min) was investigated. A total of 102 patients without severe heart or circulatory failure were randomized to receive either intravenous flecainide (2 mg/kg, maximum dose 150 mg; 51 patients) or placebo (51 patients) in a double-blind trial. Digoxin (500 micrograms intravenously) was administered to all patients who had not previously been receiving digoxin. The electrocardiogram was monitored continuously during the study. In 29 (57%) patients stable sinus rhythm was restored within 1 hour after flecainide and in only 7 (14%) given placebo (chi square 18.9; p = 0.000013; odds ratio 8.3; 95% confidence interval 2.9-24.8). Reversion to sinus rhythm within 1 hour after starting the trial medication was considered a pretrial end point and likely to be due to a drug effect. At the end of the 6-hour monitoring period, 34 patients (67%) in the flecainide group were in sinus rhythm whereas only 18 (35%) in the placebo group had reverted (chi square 8.83, p = 0.003; odds ratio 3.67; 95% confidence interval 1.5-9.1). Significant hypotension, although short lived, was more common in the flecainide group. One patient given flecainide developed torsades de pointes and was successfully electrically cardioverted. Flecainide is useful for the management of recent-onset AF both for control of the ventricular response and conversion to sinus rhythm.(ABSTRACT TRUNCATED AT 250 WORDS)

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 >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.

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

ObjectiveTo assess the role of intravascular atrial electrograms in improving the diagnosis of complex cardiac arrhythmias in critically ill patients. DesignProspective, clinical study comparing the accuracy of cardiac rhythm diagnosis using standard surface electrocardiogram (EKG) and intravascular atrial electrograms. SettingIntensive care unit of a university teaching hospital. PatientsA 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. InterventionsNone. Measurements and Main ResultsThe 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. ConclusionsIntravascular 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. (Crit Care Med 1993; 21:532–537)

Hemodynamic benefit of maintaining atrioventricular synchrony during cardiac pacing in critically ill patients

Objective.To determine the hemodynamic effects of maintaining atrioventricular synchrony during emergency cardiac pacing in critically ill patients. Design.Prospective, within patient double-blind study. Setting.ICU or coronary care unit patients in a university hospital. Patients.Forty (23 cardiac surgery, ten acute myocardial infarction, and seven general intensive care) seriously ill patients with severe symptomatic bradycardia. Intervention.Initial randomization of patients to receive either a pacing mode where atrioventricular synchronization was maintained (atrioventricular pacing: atrial demand, atrioventricular sequential, atrioventricular universal) or a mode of pacing where atrioventricular synchrony was not preserved (ventricular demand pacing). Measurements and Main Results.The cardiac output increased from a mean of 4.5 ± 1.7 L/min (95% confidence intervals: 4.0 to 5.0 L/min) during ventricular demand pacing to 5.3 ± 1.7 L/min (95% confidence intervals: 4.9 to 5.9 L/min) during atrioventricular pacing (p < .0001) despite trivial decreases in CVP from 14 ± 4 mm Hg (95% confidence intervals: 13 to 15 mm Hg) to 13 ± 5 mm Hg (95% confidence intervals: 12 to 15 mm Hg) and pulmonary artery occlusion pressure from 18 ± 5 mm Hg (95% confidence intervals: 16 to 20 mm Hg) to 17 ± 5 mm Hg (95% confidence intervals: 15 to 18 mm Hg). At the same time, mean arterial pressure (MAP) increased from 74 ± 15 mm Hg (95% confidence intervals: 64 to 79 mm Hg) to 83 ± 15 mm Hg (95% confidence intervals: 80 to 88 mm Hg) and left ventricular stroke work index from 22 ± 10 g.m/m2 (95% confidence intervals: 19 to 25 g.m/m2) to 30 ± 11 g.m/m2 (95% confidence intervals: 26 to 33 g.m/ms). There was no significant change in mean pulmonary artery pressure, pulmonary vascular resistance index, or systemic vascular resistance index. Conclusion.When cardiac pacing is required in critically ill patients, maintaining atrioventricular synchrony increases stroke volume, cardiac output, and MAP apparently with minimal effects on preload and after-load. (Crit Care Med 1991; 19:320)

Perioperative myocardial ischaemia and infarction in non-cardiac surgical patients

Summary Cardiovascular morbidity and mortality associated with non-cardiac surgery increase with the probability and severity of coronary artery disease in the surgical population. In the absence of coronary artery disease, the risk of a perioperative cardiac event is negligible. Preoperative evaluation of patients should always include a thorough history and clinical examination but specific investigations should be individualized as false-positive results are common when the incidence of coronary artery disease is low. Recent myocardial infarction, symptoms suggestive of unstable angina and the presence of heart failure are powerful predictors of perioperative cardiovascular morbidity. A routine 12-lead electrocardiogram should be obtained for all men over 40 years and for all women over 55 years as well as for all patients with a history suggestive of heart disease. Stress testing, with or without thallium, is useful for patients with peripheral vascular disease, and dipyridamole-thallium imaging may be of value in risk stratification for those patients in whom adequate exercise levels cannot be achieved. The risk of a cardiovascular event during surgery can be stratified using a ‘risk index’. Coronary angiography allows precise definition of the coronary anatomy and accurate assessment of left ventricular function but this is usually reserved for patients with severe symptoms or for those found to be at high risk as a result of provocative testing, where it is felt that revascularization of the myocardium may be indicated before the proposed surgery. Every effort should be made to treat any reversible risk factors that arepresent (unstable angina, heart failure, etc.) before surgery, with the aim of decreasing perioperative morbidity and mortality. In general, all cardiac medications should be continued throughout the perioperative period unless specific complications occur necessitating their withdrawal. Throughout the stress of the perioperative period myocardial oxygen delivery must be maintained while myocardial oxygen consumption should be kept at a low level. Myocardial ischaemia is common in patients with coronary artery disease during anaesthetic inducation and perioperative infarction occurs largely in those patients who develop significant tachycardia, hypotension or hypertension during surgery, the risk of infarction being increased three-fold when perioperative ischaemia occurs. Monitoring of the cardiac rhythm, arterial pressure, ST segment changes and, in high-risk patients, more sophisticated parameters of cardiac function, will allow for the early diagnosis of myocardial ischaemia and allow therapy to be monitored. Anaesthetic risk cannot be eliminated but can be minimized. The anaestheticagents and technique can be tailored to a patients cardiovascular status but much will also depend on the anaesthetists experience and expertise. Even with the best management there will be circumstances when myocardial ischaemia and infarction will occur and successful management will depend upon recognition and treatment. Careful monitoring can help diagnose myocardial ischaemia but infarction may be difficult to diagnose unless there is a high index of suspicion. It is often not possible to obtain a history and the standard investigations such as the 12-lead electrocardiogram and cardiac enzymes can be difficult to interpret. Radionuclide techniques and echocardiography can be helpful. The initial treatment of myocardial ischaemia and infarction in the perioperative period is identical, with nitrates, β-blocking drugs, aspirin and calcium antagonists being used. Thrombolytic therapy is contraindicated during and immediately after surgery. A combination of improved anaesthetic agents and techniques, togetherwith advances in the treatment of coronary artery disease, appear to be making surgery safer for patients with heart disease.