Anzhen Qi

Atrial flutter in patients treated for atrial fibrillation with propafenone

Abstract The class IC antiarrhythmic drug, propafenone, has been used successfully for the prevention of atrial fibrillation (AF), with few reported adverse cardiovascular effects. 1–3 Propafenone depresses the rate of rise and amplitude of phase 0 of the action potential, slowing conduction in the atrium. 4 Although it has mild β-adrenergic antagonist effects, it has relatively less effect on atrioventricular refractoriness, although in AF the ventricular response may slow. 5 With slower atrial arrhythmias such as atrial flutter, where less concealment of conduction occurs, it is possible that the same effect on ventricular rate may not be seen. This study defines the incidence of atrial flutter developing in a heterogeneous population of patients with recurrent AF and observes the ventricular response during this arrhythmia.

Nonsustained ventricular tachycardia arising from the right ventricular outflow tract

Characteristics of left bundle branch block morphology, inferiorly directed frontal plane QRS axis and repetitive nonsustained salvos were used to define a discrete subgroup of patients with ventricular tachycardia (VT). The origin of this tachycardia was thought to be the right ventricular outflow tract. Twenty-six patients with this definition (group 1) were compared with 29 consecutive patients with all other forms of VT (group 2). When compared with patients in group 2, group 1 patients were younger (average age 37 vs 51 years, p less than 0.005), had less structural heart disease (2 of 26 vs 25 of 29 patients, p less than 0.005) and had a better prognosis (no deaths) after an average follow-up time of 28 months in comparison with 5 deaths after an average follow-up of 35 months (p less than 0.05). Induction of VT was possible using isoproterenol infusion in 14 of 20 group 1 patients, but no VT could be induced in 9 group 2 patients (p less than 0.05). Exercise stress testing induced VT in 11 of 21 group 1 patients and 2 of 9 group 2 patients (p greater than 0.05). Programmed electrical stimulation failed to induce VT in 9 group 1 patients, but did induce it in 15 of 20 group 2 patients (p less than 0.005). Successful therapy in group 1 patients was achieved by beta blockers alone (7 patients), beta blockers plus type 1A antiarrhythmic drugs (9 patients), procainamide alone (2 patients), sotalol (3 patients) and amiodarone (2 patients). Three patients were not treated.(ABSTRACT TRUNCATED AT 250 WORDS)

Prognostic impact of inappropriate defibrillator shocks in a population cohort

Background There is a relative paucity of data linking inappropriate implantable cardioverter-defibrillator (ICD) shocks to adverse clinical outcomes. Objective To examine the association between inappropriate ICD shocks and mortality or heart transplantation in a large population cohort. Design, setting, patients A cohort study which included all subjects who underwent ICD implantation between 1998 and 2008 and were followed up at our institution. Main outcome measures Multivariable Cox regression analyses were conducted to investigate the effect of inappropriate shocks on the risk of death and heart transplantation. Appropriate and inappropriate ICD therapies were modelled as time-dependent covariates. Results A total of 1698 patients were included. During a median follow-up of 30 months, there were 246 (14.5%) deaths and 42 (2.5%) heart transplants. The incidence of inappropriate shocks was 10% at 1 year and 14% at 2 years. In the adjusted model, inappropriate shocks were not associated with death or transplantation (HR=0.97, 95% CI 0.70 to 1.36, p value=0.873). In contrast, appropriate shocks were associated with adverse outcomes (HR=3.11, 95% CI 2.41 to 4.02, p value<0.001). The lack of association between inappropriate shocks and outcomes persisted for those with severely impaired left ventricular function (ejection fraction <30%) and for those receiving multiple inappropriate treatments. Conclusions In this study, we observed no association between inappropriate ICD shocks and increased mortality or heart transplantation, even among those with severely impaired cardiac function. These findings question whether inappropriate ICD shocks lead to adverse outcomes.

Initial experience with a co-radial bipolar pacing lead.

A new type of endocardial bipolar pacing lead has been designed to overcome the potential drawbacks of the conventional coaxial bipolar pacing had. We prospectively evaluated the new co‐radial bipolar pacing leads (Intermedics Thin Line), which are thinner (5 Fr vs 6—8 Fr) than standard coaxial bipolar leads. X‐ray visibility and lead handling were subjectively assessed (excellent, good, adequate, or poor) at implant; lead impedance, sensitivity threshold, and pacing threshold were measured at implant, then at 1, 3. 6, 12, and 18 months. The results were as follows: 103 patients (51 M; age 63.8 ± 17.4 years) received 71 atrial (A) and 89 ventricular (V) leads. X‐ray visibility was excellent in 59/103; good in 23/103; adequate in 11/103; and poor in 10/103. Overall handling was excellent in 56/71 A and 69/89 V; good in 11/71 A and 18/89 V; adequate in 3/71 A and 1/89 V; poor in 1/71 A and 1/89 V. There were two perioperative complications. At implant: impedance in A and V were 370.1 ± 74.7 and 501.5 ± 124.4 Ω, sensing thresholds in A and V were 3.0 ± 1.5 and 9.9 ± 5.0 mV, pacing thresholds at 0.45 ms in A and V were 0.59 ± 0.21 and 0.41 ± 0.15 volt, respectively. At 1, 3, 6. 12, and 18 months of follow‐up: no pacing lead related complications were reported; pacing lead characteristics remained outstanding and stable. This new lead appears to have significant clinical advantages over the conventional coaxial bipolar pacing lead. Long‐term follow‐up is required to confirm its reliability and chronic performance characteristics.

Long-Term Survival Following Radiofrequency Catheter Ablation of Atrioventricular Junction for Atrial Fibrillation: Clinical and Ablation Determinants of Mortality

AbstractBackground: For patients with drug-refractory atrial fibrillation, radiofrequency catheter ablation of the atrioventricular junction and pacemaker implantation is a nonpharmacologic option routinely used nowadays. Few data are available on the long-term survival following the procedure or on evaluation of the risk factors for death in a large study cohort. Methods: The patient population included 359 subjects undergoing atrioventricular junction ablation and pacemaker insertion. Fourteen clinical and 9 ablation variables were collected at baseline. During a mean following-up of 40.8±25.6 months, 46 patients died. Survival probability was estimated by the Kaplan-Meier methods. Multivariate Cox proportional hazards regression analysis was applied to define predictors of death. Results: Mean age was 64.6±10.6 years with 203 male (57.7%). Actuarial survival probability for the total patients was 0.953 and 0.827 at 1 and 5 year. Four clinical variables, but no ablation variables, were found to be independent predictors of death: age ≥65 year (hazard ratio [HR], 1.92; 95% confidence interval [CI], 1.00–3.69), the presence of heart failure (HR, 3.83; 95% CI, 1.87–7.86), coexisting diabetes (HR, 2.91; 95% CI, 1.47–5.77), and the value of fractional shortening ≤20% (HR, 5.79, 95% CI, 3.00–11.18). There were 20 deaths in 28 patients with ≥3 risk factors and 4 deaths in 115 patients with no risk factor. Conclusion: The risk of death in patients undergoing ablation and pacing can be identified by readily available clinical variables. Patients with multiple risk factors are associated with an increasing mortality.

Pacing in right ventricular dysplasia after disconnection surgery.

Pacing in Right Ventricular Dysplasia. This report describes a 33‐year‐old patient with arrhythmogenic right ventricular (RV) dysplasia who had a dual chamber pacemaker implanted at age 23 years for drug‐induced bradycardia. Pacing was continued after right ventricular free‐wall disconnection (RVFVVD) at age 24 years. Her pacemaker was not replaced after battery depletion 7 years later. She presented the following year in severe right‐sided heart failure. Her old pacemaker generator was replaced. This was followed by rapid resolution of her clinical failure and return to a full, active, physical lifestyle. This observation suggests the potential benefit of dual chamber pacing in patients with RV dysplasia after RVFWD.

Symptomatic sinus node dysfunction associated with the use of propafenone

Propafenone is an investigational antiarrhythmic agent with demonstrated effectiveness against a variety of supraventricular and ventricular arrhythmias.1 In vitro and in vivo studies have confirmed its class I activity in suppressing the rate of rise of phase 0 of the action potential by blocking the fast inward sodium current.2 In addition, propafenone has a mild β-blocking effect. Clinically the drug has been shown to slow sinus rate3 and prolong the sinus node recovery time.4 However, advanced sinus node dysfunction leading to symptomatic bradycardia associated with the use of propafenone has been rarely reported. Herein, we report 6 such cases presenting over 3 years.

pH-dependent actions of 4-aminopyridine on atrial repolarization: effects on the transient outward current

Effects of extracellular pH (pHo) were examined on the changes in atrial repolarization induced by 4-aminopyridine (4AP), which is a selective blocker of the transient outward potassium channel, I(to). Action potential parameters were measured, using the conventional microelectrode technique, in the absence and presence of 4AP (0.1-3.0 mM) at pHo 6.5, 7.25, and 8.0. Phase 1 amplitude served as an index of I(to). The onset and recovery kinetics of phase 1 amplitude were assessed at a basic cycle length of 0.5 s, and time constants (tau on and tau r) were computed. Both onset and recovery kinetics had monoexponential functions. Tonic blockade was influenced by external pH, and Kd for half block was 0.19, 0.44, and 2.43 mM for pHo 8.0, 7.25, and 6.5, respectively. Phasic block was defined and exhibited cycle length dependence. Phasic block was also modified by external pH with the greatest effect at pHo 8.0. 4AP (0.3 mM) accelerated tau on, 0.62 +/- 0.2, 0.55 +/- 0.1, and 2.0 +/- 0.8 beats for pHo 8.0, 7.25, and 6.5 compared with control 6.8 +/- 1.9, 6.3 +/- 1.9, and 5.1 +/- 1.4 beats. In contrast, 4AP slowed tau r by about 1 s from control value to 1.5 +/- 0.5 s at pHo 6.5, 4.8 +/- 1.5 s at pHo 7.25 (p < 0.05), and 5.7 +/- 2.0 s at pHo 8.0. We conclude that an increase in extracellular pH enhances block of Ito induced by 4AP, whereas low pHo attenuates the block.