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Background Advances in implantable cardioverter defibrillator (ICD) technology have resulted in more effective defibrillation, and the need for defibrillation threshold (DFT) testing has been questioned. Methods A total of 64,227 initial ICD implant procedures performed at 1,261 facilities (April to December 2010) in the NCDR Registry™ were selected to identify patterns of practice related to DFT testing. Patient, physician, and procedural characteristics were compared. Independent association of DFT testing with in-hospital adverse events or mortality was also examined. Results DFT testing was performed in 71% of patients. Patients who did not undergo testing were older; more often had heart failure, lower left ventricular ejection fraction, atrial arrhythmias, and a primary prevention indication; and were more likely to receive a cardiac resynchronization therapy device. In addition, patients who did not undergo testing were less likely to be implanted in a metropolitan area and more often implanted at a teaching hospital, in New England, in the Mid-Atlantic, or in the Pacific U.S . In-hospital adverse events occurred in 2.56% of patients who underwent DFT testing compared to 3.58% who did not (P < 0.001). Death or any complication remained more likely to occur in patients who did not undergo testing (odds ratio and 95% confidence interval: 1.46 [1.33, 1.61], P < 0.001), after adjusting for baseline and procedural differences. Conclusions DFT testing is not performed in many (29%) patients in clinical practice. Patients who did not undergo testing were more likely to have adverse events and to be older with more comorbidities, which could explain why DFT testing was avoided. Prospective randomized data are needed to determine the impact of DFT testing on outcome.

Background: Primary prophylaxis with implantable cardioverter-defibrillators (ICDs) improves mortality in patients at risk for sudden cardiac death (SCD). However, ICDs are highly underutilized. We explored patients’ attitudes and perceptions of ICDs to better understand potential patient-related barriers to appropriate utilization. Methods: Records of patients visiting three outpatient cardiology clinics (June 2009–January 2010) were reviewed and 133 with ejection fractions ≤35% and without an ICD were identified. Seventy-two met criteria for ICD placement. Twenty-five consented and were interviewed by telephone using a semistructured open-ended interview guide. Twelve individuals had accepted ICD referral, and 13 had declined. We analyzed transcripts of ICD refusers and acceptors using the constant comparative method of grounded theory. Results: Five major themes emerged: (1) Patients who refused ICD referral demonstrated a lack of insight into their own risk potential. (2) Many patients who accepted ICD referral perceived that this was strongly recommended by their physicians, although many patients refusing did not. (3) Concerns over recall, malfunction, and surgical risk were common in both. (4) Many patients demonstrated inaccurate perceptions of ICD-related risks and lifestyle changes. Acceptors often reported these perceptions being addressed by their physician. (5) Feelings regarding invasive life-prolonging interventions played an important role in ICD referral refusal for some individuals. Conclusions: Refusal of ICD is common among primary prevention candidates. Common themes in the decision-making process include insight into personal risk of SCD, and perceived strength of the physician recommendation. Providers may want to consider assessment of patients’ individual understanding and perceptions when discussing ICD prophylaxis. (PACE 2012; 35:1179–1187)

Background: Electrophysiology studies (EPS) have historically played a role in sudden death risk stratification. More recent studies point to the left ventricular ejection fraction (EF) as a guide to implantable cardioverter defibrillators (ICD) implantation. The extent of EPS use in patients undergoing ICD implantation in the current era remains unknown. Methods: Patients undergoing de novo ICD implantation in the ICD Registry between September 2006 and March 2009 who also underwent EPS within 30 days before implant were compared to the remaining cohort to identify clinical characteristics that correlated with EPS performance. Multivariate models were generated using hierarchical logistic regression analysis. Results: EPS were performed in 33,786 of 275,273 patients. Those undergoing EPS were more likely to have had a history of syncope, family history of sudden death, lack of congestive heart failure, narrower QRS intervals, and higher EF. Overall, 63.9% of EPS were performed in patients receiving primary prevention ICDs. Ventricular tachyarrhythmias were induced in 46.1% of primary prevention and 54.2% of secondary prevention ICD recipients. Monomorphic ventricular tachycardia was the most common type of arrhythmia induced in both groups. Complication rates were not higher in those undergoing EPS. Conclusions: EPS were performed predominantly in patients with borderline or less well-defined risk factors for sudden death. Ventricular arrhythmias induced from EPS were not uncommon and may help identify individuals at higher risk for future ICD therapies. Efforts to better define the role of EPS in patients undergoing ICD implantation should be considered. (PACE 2012; 35:912–918)

Background: Symptoms are among the most important factors impacting quality of life (QOL) in hypertrophic cardiomyopathy (HCM) patients, and reflect a poor prognosis. Whether emotional stress can trigger symptoms of chest pain, dyspnea, palpitations, and lightheadedness has not been described. Methods: Members of the Hypertrophic Cardiomyopathy Association (HCMA) received an electronic link via e-mail to an ongoing online survey, also accessed via links on the HCMA message-board and homepage. Between May 2007 and November 2008, there were 1,297 respondents. The survey queried demographic and self-reported clinical information, and types and triggers of symptoms. Respondents reported physical and emotional QOL on a 1–10 Likert scale. Results: Symptoms reported included chest pain (49%), dyspnea (70%), palpitations (61%), and syncope/lightheadedness (59%). The most common symptom trigger was exertion, 64% describing symptoms while climbing stairs or hills. Forty-nine percent described experiencing symptoms during emotional stress. Those reporting chest pain were more likely to report emotion triggering (60%) than those reporting palpitations, syncope/lightheadedness, or dyspnea (50–54% each). Both physical and emotional QOL were significantly decreased in those describing emotion-triggered symptoms. Women were more likely than men to report symptoms overall, as well as emotion-triggered symptoms (50% vs 35%, P < 0.001) and exertion-triggered symptoms (79% vs 58%, P < 0.001). After controlling for presence of symptoms, both emotion- and exertion-triggered symptoms remained significantly more common in women. Conclusions: Triggering of symptoms by emotion is common in individuals with HCM. Further studies will determine pathways linking emotional stressors with chest pain, dyspnea, palpitations, and lightheadedness in these patients. (PACE 2010; 33:1047–1053)

Although the problem of ICD sensing of paced ventricular stimuli has been resolved by incorporation of VVI pacing into current ICDs, many patients required separate DDD pacemakers. We report a problematic PM-ICD interaction: the inability to prevent sensing of paced atrial stimuli ("atrial sensing") leading to double-counting in DDD-PM-requiring patients with transvenous (TV) ICDs with aggressive autogain sensing (CPI Ventak PRxII or III). Four of eight patients receiving both transvenous DDD PMs and ICDs (CPI Endotak lead, at the RV apex), had atrial sensing, leading to double counting, despite intraoperative testing of multiple atrial locations with an active fixation lead. Five patients had a PRxII/III ICD, four with atrial sensing (80%), and three a PRx without atrial sensing. Patients with atrial sensing were not distinguished by any clinical or device related variable. In patients with atrial sensing (all with heart block), the PM was programmed to VDD mode. No patient has received inappropriate therapy or failed to sense VF in follow-up. In many patients with TV ICDs who required DDD pacing, no atrial position can be found without ICD sensing of atrial stimuli. While in patients with heart block this problem can be circumvented by programming to the VDD mode, in patients with sinus incompetence it may only be resolved by the combination ICD-DDD PM, currently in development.

The CPI PRxII is a recently approved, multitiered implantable cardioverter defibrillator (ICD) that delivers high and low energy biphasic shocks, antitachycardia (ATP) and bradycardia pacing, and stores 2.5 minutes of electrograms from the widely spaced shocking electrodes. The PRxII was implanted in 58 patients at Yale-New Haven Hospital between December 1993 and January 1995. At implant, mean biphasic defibrillation threshold (DFT) in patients with testing to failure was 10 J (1-20). All 36 patients who were candidates for a new transvenous system underwent successful nonthoracotomy implantation. Based on noninvasive predischarge EPS results, 30 patients had > or = 1 VT zone: 21 patients had ATP, 9 others had first shock < or = 5 J. During follow-up, 13 patients had been treated for 379 events (range, 1-127). Of 340 events in a zone with ATP, 97% responded to ATP, 3% required shock. First programmed shock converted all events in a VF zone. Details, including RR intervals, were available for all events in 15 of 17 patients receiving appropriate or inappropriate therapy or diverted shocks. One hundred eleven of 148 available electrograms confirmed VT by morphology, rate, and/or presence of AV dissociation. In nine patients, electrogram data altered therapy through diagnosis of inappropriate or diverted therapy, guidance of detection enhancements, or diagnosis of previously unrecognized VTs. We conclude the PRxII achieves low DFTs that obviate the need for thoracotomy and effectively treats ventricular arrhythmias with ATP and shock, with programming guided by noninvasive electrophysiology. Multiple stored electrograms from widely spaced shocking electrodes greatly enhance diagnostic capabilities, facilitating effective treatment.