Gregory W. Woo

Ventricular Reverse Remodeling and 6-Month Outcomes in Patients Receiving Cardiac Resynchronization Therapy: Analysis of the MIRACLE Study

Objective: The objective of this analysis was to determine if there were differences in ventricular reverse remodeling and 6-month outcome with cardiac resynchronization therapy (CRT) among specific subgroups enrolled in the Multicenter InSync Randomized Clinical Evaluation (MIRACLE) Study.Background: Analysis of major subgroups receiving CRT is important in determining who may be most likely to benefit, since all patients who receive CRT do not demonstrate improvement.Methods: Differences in response to CRT between subgroups based on baseline echocardiographic parameters, New York Heart Association (NYHA) class, age, gender, beta blocker use, and etiology of heart failure (HF) were analyzed for the clinical end points of the study as well as 6-month HF re-hospitalization or death.Results: The benefit of CRT over control was similar in all subgroups with respect to all clinical endpoints. However, non-ischemic HF patients had greater improvements with CRT compared to ischemic HF patients in left ventricular end diastolic volume (P < 0.001) and ejection fraction (EF) (6.7% increase vs. 3.2% [P < 0.001]). Greater improvements in EF were also seen in those patients with less severe baseline mitral regurgitation (MR) (P < 0.001). Women but not men receiving CRT were more likely to be event-free from first HF hospitalization or death compared to the control group (Hazard Ratio = 0.157).Conclusions: The benefits of CRT with respect to EF and reverse remodeling were greater in patients with non-ischemic HF and less severe MR. Women may also derive more benefit than men with respect to the occurrence of HF hospitalization or death.

Appropriate Evaluation and Treatment of Heart Failure Patients After Implantable Cardioverter-Defibrillator Discharge: Time to Go Beyond the Initial Shock

Multiple clinical trials support the use of implantable cardioverter-defibrillators (ICDs) for prevention of sudden cardiac death in patients with heart failure (HF). Unfortunately, several complicating issues have arisen from the universal use of ICDs in HF patients. An estimated 20% to 35% of HF patients who receive an ICD for primary prevention will experience an appropriate shock within 1 to 3 years of implant, and one-third of patients will experience an inappropriate shock. An ICD shock is associated with a 2- to 5-fold increase in mortality, with the most common cause being progressive HF. The median time from initial ICD shock to death ranges from 168 to 294 days depending on HF etiology and the appropriateness of the ICD therapy. Despite this prognosis, current guidelines do not provide a clear stepwise approach to managing these high-risk patients. An ICD shock increases HF event risk and should trigger a thorough evaluation to determine the etiology of the shock and guide subsequent therapeutic interventions. Several combinations of pharmacologic and device-based interventions such as adding amiodarone to baseline beta-blocker therapy, adjusting ICD sensitivity, and employing antitachycardia pacing may reduce future appropriate and inappropriate shocks. Aggressive HF surveillance and management is required after an ICD shock, as the risk of sudden cardiac death is transformed to an increased HF event risk.

Incidence, Predictors, and Outcomes of Cardiac Pacing After Cardiac Transplantation : An 11-Year Retrospective Analysis

More than 20% of cardiac transplant patients go on to require permanent pacing. We sought to determine the incidence of cardiac pacing in our cardiac transplant population and identify characteristics that may predict which patients will require permanent pacing. We reviewed medical records of cardiac transplant recipients and compared baseline characteristics of patients who received pacemakers with those of patients who did not receive pacemakers. Of 292 patients included in this analysis, 71 (24%) required permanent posttransplant pacing. Use of amiodarone before transplant was associated with a nonsignificant trend toward needing a pacemaker after transplant (P=0.08). Patients undergoing biatrial anastomosis were more likely to require permanent pacing than patients undergoing bicaval anastomosis (P<0.001). Approximately one fourth of cardiac transplant patients require permanent pacing. Surgical technique is a major predictor of who will require permanent pacing after cardiac transplantation.

Minimally invasive ablation of a migrating focus of inappropriate sinus tachycardia.

CLINICAL SUMMARY A 31-year-old echocardiography technician experienced tachycardia after pregnancy 3 years before presentation. The patient reported symptoms of dizziness, shortness of breath, and fatigue. An echocardiogram revealed an ejection fraction of 65% and mild mitral valve prolapse. Twentyfour-hour Holter monitoring showed a resting heart rate between 70 and 175 beats/min with rare premature ventricular complexes and rare atrial premature complexes with no evidence of sinoatrial or atrioventricular nodal block. Metoprolol, atenolol, sotalol, digoxin, and amiodarone therapy had failed. Prior catheter-based ablation attempts had mapped the focus of tachycardia laterally at the superior vena cava and right atrial junction. The catheter ablation attempts were able to modify the heart rate; however, they were aborted because of proximity of the right phrenic nerve. Subsequently, she was referred for a minimally invasive thoracoscopic isolation of the sinus node using a dry bipolar radiofrequency energy clamp (AtriCure, West Chester, Ohio). Port sites were placed at the fifth interspace in the anterior axillary line and the sixth interspace in the posterior axillary line, and a 5-cm incision was made in the mid-axillary third interspace. The pericardium was opened, and adhesions from the catheter ablations were found lateral to the superior vena cava in the vicinity of the phrenic nerve. An isoproterenol infusion (4 mg/min) was started, which elevated the resting heart rate to 140 beats/min. The superior vena cava was then dissected free and the entire sinoatrial node complex was encircled with the radiofrequency clamp, which was applied multiple times with no change in the resting heart rate, although pacing confirmed transmural ablation lines (Figure 1). Subsequently, a reference electrode was sutured medial to the superior vena cava at the right atrial junction (Figure 2),