Biomedical subjects
Publications and source records attributed to R G Trohman.
An abrupt decrease in the pacing rate in patients with dual-chamber pacemakers tracking atrial tachyarrhythmias carries a high risk of malignant ventricular arrhythmia. The pacing rate should be reduced by multistep programming over several days.
Significant advances have been made in the management of cardiac arrhythmias. New technology has enhanced the ability to understand and treat a variety of tachycardias. Excitement and caution surround ablative approaches for atrial fibrillation. The role of ICDs and class III antiarrhythmic drugs in the management of patients at risk for sudden cardiac death has been clarified. A new indication for cardiac pacing is evolving as a supplemental treatment for patients with refractory congestive heart failure. These and other advances provide numerous exciting options for management of cardiac patients.
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BACKGROUND: Intravenous amiodarone is effective for the acute suppression of recurrent hemodynamically destabilizing ventricular arrhythmias. There are no follow-up data on patients undergoing long-term therapy with intravenous amiodarone. The objective of this investigation was to evaluate long-term outcome. METHODS AND RESULTS: We reviewed the clinical courses of 245 patients given intravenous amiodarone for sustained ventricular tachyarrhythmias. Of the 107 survivors (84% men; mean age 64 years) released from the hospital taking oral amiodarone, 41 were discharged with an empiric prescription for oral amiodarone. For 64 patients a decision regarding further therapy was based on results of an electrophysiologic study. Two patients were treated empirically with oral amiodarone and an implantable cardioverter defibrillator. Clinical variables and survival curves were the same for the empirically treated group and the group whose treatment was based on electrophysiologic findings (P =.89). Survival at 6, 12, and 18 months was 88%, 81% and 71%, respectively, for empirically treated patients, and 83%, 80% and 73%, respectively, for patients whose therapy was directed with an electrophysiologic study. Of the 64 patients who underwent electrophysiologic studies, 33 received an implantable cardioverter defibrillator. The Kaplan-Meier survival curves for patients with and patients without an implantable cardioverter defibrillator were similar (P =.46). CONCLUSIONS: Patients for whom recurrent ventricular tachycardia and fibrillation are suppressed with intravenous amiodarone and who are discharged receiving oral amiodarone have an 80% 1-year survival rate. Although not randomized, our data suggested that among such patients, electrophysiologic testing, implantation of a cardioverter defibrillator, or both may not be necessary. Ascertaining the best management strategy for these patients will require a prospective randomized trial.
Most exposures to electromagnetic interference are transient and pose no threat to patients with pacemakers and implantable cardioverter defibrillators. Prolonged exposure may be catastrophic in pacemaker dependent patients. New technologies (wireless phones, electronic antitheft surveillance) are safe if proper precautions are takes. Radiofrequency ablation requires concomitant temporary pacing. MR imaging remains contraindicated in patients with these devices until further study is undertaken.
A 66-year-old man with coronary artery disease and persistent left superior vena cava received a DDDR pacemaker for symptomatic 2:1 heart block. There was no previous history of tachyarrhythmias. Endless loop tachycardia and repetitive nonreentrant ventriculoatrial synchrony occurred afterwards and were triggered by a late coupled atrial premature beat. ECGs suggested a concealed left posterior accessory pathway that was confirmed during electrophysiological study. Effective palliation was achieved with extension of the PVARP and enabling noncompetitive atrial pacing operation.
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Bradycardia is common in critical care units. It may be transient, asymptomatic and of little consequence, or life-threatening. Bradycardia may result from abnormalities of the sinus node, atrioventricular node, or the His-Purkinje system. It may also be precipitated by drug effects or enhanced vagal tone. Proper diagnosis is pivotal to determining prognosis and management. Temporary and permanent pacing is now readily available, markedly improving the morbidity and mortality associated with bradyarrhythmias.
The critical care physician must have a keen awareness of supraventricular tachycardia patterns, mechanisms, precipitants, and treatment. Although long-term management of most forms of supraventricular tachycardia lies primarily in the realm of the cardiac electrophysiologist, the intensivist must be proficient at acute arrhythmia therapy. Expertise in electrocardiography, pharmacokinetics, and pharmacodynamics is essential. Careful assessment of hemodynamics and prudent bedside clinical acumen help assure optimal patient outcomes.
Direct current cardioversion/defibrillation is an important part of the intensivist's armamentarium. Emergent application may be lifesaving. Elective cardioversion should be used cautiously, with attention to patient selection and proper techniques. Repetitive, futile attempts at direct current cardioversion should be avoided. Reducing or eliminating arrhythmia precipitants may be safer and more effective than this more dramatic intervention.
It is desirable to maintain normal, conducted ventricular activation in patients with dual-chamber pacemakers and preserved atrioventricular (AV) conduction. The shortest AV delay resulting in consistent ventricular inhibition (avoiding ventricular pseudofusion) was determined by a conventional incremental (inside-out) technique vs the alternate decremental (outside-in) technique in 20 such patients. Determinations were made in VDD mode in 20 patients and DDD mode (approximately 10 beats/min faster than the intrinsic rate) in 19. In VDD mode, the shortest AV delay avoiding ventricular pseudofusion was never found during inside-out testing. It was identical with both methods in 10 patients (50%), and shorter by 10-80 ms (mean 20 +/- 20 ms) with the outside-in method in the remaining 10 (P = 0.004). In DDD mode, the shortest AV delay resulting in consistent ventricular inhibition was found only once during inside-out testing. It was the same with both methods in 13 patients (68%), and shorter by 10-20 ms (mean 14 +/- 5 ms) with the outside-in method in the remaining 5 (26%, P = 0.18; Fisher's exact test). The shortest sensed AV delay preventing ventricular pseudofusion is most likely to be found with a decremental method (outside-in). In rare patients, it identifies AV delays resulting in inhibition, while ventricular pacing persists at longer programmable AV delays with the conventional inside-out approach.
BACKGROUND: Direct-current cardioversion remains the gold standard for restoration of sinus rhythm in patients with atrial flutter. Although an initial energy of 50 J is recommended, the optimal energy settings have not been evaluated in a large series of contemporary patients. METHODS: We compared the outcome of cardioversion with 50 J versus 100 J in 330 consecutive patients with atrial flutter. Initial energy was based on attending physician preference. One hundred sixty patients received 50 J and 170 patients received 100 J. RESULTS: Patients in both groups did not differ significantly in age, sex, weight, body mass index, duration of the arrhythmia, postoperative status, presence and type of structural heart disease, or use of antiarrhythmic drugs. Patients in the 100-J group had more first shock conversion (85% vs 70%; P =. 001), fewer total shocks (1.2 +/- 0.5 vs 1.4 +/- 0.7; P =.001), and less induction of atrial fibrillation (2% vs 11%; P =.002). There were no significant differences in overall restoration of sinus rhythm, cumulative energy delivered, anesthetic dose, and procedure room time. On multivariate analysis, delivery of 100 J was the strongest predictor of first shock success (odds ratio 2.6, 95% confidence interval 2.13 to 3.16; P <.001). CONCLUSION: An initial energy of 100 J is more efficient for restoration of sinus rhythm in patients with atrial flutter.
We report a case of successful radiofrequency catheter ablation of recurrent atrial flutter in a heart transplant recipient and discuss technical aspects of the procedure. A counterclockwise flutter circuit was defined during endocardial mapping of the donor atrium. Termination of atrial flutter was achieved by creating lines of radiofrequency lesions from the tricuspid ring to the suture line between donor and recipient atria. Creation of bidirectional conduction block in the tricuspid ring-suture line isthmus resulted in abolition of atrial flutter.
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A 33-year-old woman with congenital heart disease and atrial and ventricular arrhythmias, managed over the long term with an implantable cardioverter defibrillator, epicardial pacing system, and amiodarone, experienced an increase in palpitations and a shock from her defibrillator. Evaluation revealed decreases in amiodarone and desethylamiodarone serum concentrations from previous levels. Rifampin had been added to her therapy 5 weeks earlier. Increases in amiodarone and desethylamiodarone concentrations were observed after an increase in the amiodarone dosage and discontinuation of rifampin. The time course suggested that the addition of rifampin led to reductions in serum concentrations of both the drug and metabolite.
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