The relation of ventricular arrhythmia electrophysiological characteristics to cardiac phenotype and circadian patterns in hypertrophic cardiomyopathy.

BACKGROUND: The triggers of ventricular arrhythmias (VAs) leading to sudden cardiac death in hypertrophic cardiomyopathy (HCM) are ill defined. We sought to examine the electrophysiological characteristics of VAs in HCM and study their relation to cardiac phenotype and circadian patterns using stored intracardiac electrocardiograms from implantable cardioverter defibrillators (ICDs). METHODS AND RESULTS: A single centre, observational cohort study of 230 consecutively evaluated ICD recipients with HCM [median age 42 years, 97% primary prevention, 51% with anti-tachycardia pacing (ATP)]. Fifty-six non-clustered VAs (39 initially treated with ATP and 17 with shocks) from 29 patients were analysed. Monomorphic ventricular tachycardia was the culprit arrhythmia in 86% of cases, ventricular fibrillation/flutter in 9%, and polymorphic ventricular tachycardia in 5%. Prior to the onset of VA the rhythm was sinus in 67%, atrial fibrillation/flutter in 19%, and 15% were paced ventricularly; tachycardia (cycle length <600 ms) was present in 25%. Ventricular arrhythmias were triggered by premature ventricular complexes (PVCs) in 72%, which were late-coupled (84%). Short-long-short initiation was seen in 2% and 26% of VAs were sudden-onset without preceding PVCs. Ventricular arrhythmia peaked at midday (with 20% occurring between 2300 and 0700), on Sundays and in May. The cardiac phenotype and time of the day did not predict the mode of initiation. Age at ICD implantation was the only independent predictor of VA cycle length (linear regression coefficient 0.67, 95% CI 0.02-1.32, P= 0.04). Anti-tachycardia pacing terminated 67% of VAs, but patients with ATP therapy had a similar incidence of appropriate shocks (log-rank test P= 0.25) and syncope (log rank P= 0.23) to patients with shock as initial therapy. CONCLUSIONS: Most VAs are monomorphic ventricular tachycardias triggered by late-coupled PVCs. They are frequently terminated by ATP, but ATP does not reduce the frequency of ICD shocks. Younger HCM patients have more rapid VAs, which may explain the peak of sudden cardiac death in early adulthood. The circadian periodicity is different from that observed in ischaemic heart disease, and is likely to relate to the distinct character of the arrhythmogenic substrate in HCM and its modulators.

The long-term survival and the risks and benefits of implantable cardioverter defibrillators in patients with hypertrophic cardiomyopathy.

OBJECTIVE: Implantable cardioverter defibrillators (ICDs) are routinely used to prevent sudden cardiac death (SCD) in selected hypertrophic cardiomyopathy (HCM) patients, but the determinants of device-related complications, therapies and long-term cardiovascular mortality in ICD recipients are not known. DESIGN: Retrospective observational cohort study. SETTING: Single-centre tertiary referral cardiomyopathy clinic. Patients 334 consecutively evaluated HCM patients (median age 40 years, 62% male, 92% primary prevention) at risk of SCD treated with ICD. Thirty-six patients (11%) received concurrent cardiac resynchronisation therapy for heart failure symptoms. RESULTS: During the 1286 patient-years of follow-up, cardiovascular mortality (including transplantation) occurred in 22 (7%) patients (1.7%/year) and was associated with New York Heart Association (NYHA) class III/IV (adjusted HR=9.38, 95% CI 3.31 to 26.55, p≤0.001), percentage fractional shortening (HR=0.92, 95% CI 0.87 to 0.96, p=0.001) and implantation for secondary prevention (HR=0.07, 95% CI 0.01 to 0.86, p=0.04). There were no SCD. Twenty-eight (8%) patients received appropriate shocks (2.3%/year), which were predicted by baseline fractional shortening (HR=0.96, 95% CI 0.92 to 0.99, p=0.04). Fifty-five (16%) patients received inappropriate shocks (4.6%/year). Sixty (18%) patients experienced implant-related complications (5.1%/year), including two deaths. Adverse ICD-related events (inappropriate shocks and/or implant complications) were seen in 101 (30%) patients (8.6%/year). Patients with cardiac resynchronisation therapy were more likely to develop implant complications than those with single-chamber ICDs (HR=4.39, 95% CI 1.44 to 13.35, p=0.009) and had a higher 5-year cardiovascular mortality than did the rest of the cohort (21% vs 6%, p<0.001). CONCLUSIONS: HCM patients with an ICD have a significant cardiovascular mortality and are exposed to frequent inappropriate shocks and implant complications. These data suggest that new strategies are required to improve patient selection for ICDs and to prevent disease progression in those that receive a device.

Treatment of Eikenella corrodens and Actinomyces odontolyticus foot abscess in a penicillin-allergic patient.

OBJECTIVE: To report a case of Eikenella corrodens and Actinomyces odontolyticus foot abscess secondary to a toothpick puncture in a penicillin-allergic patient that was successfully treated with a long-term course of doxycycline. CASE SUMMARY: A 39-year-old woman with diabetes mellitus type 2 and hyperlipidemia presented with difficulty ambulating as well as pain and swelling of her right foot. Prior to presentation, she sustained a toothpick puncture to her right foot; she removed the toothpick intact and did not know whether it had been used. Due to a penicillin allergy, she began treatment with levofloxacin, which was changed to clindamycin one day later. The patient was diagnosed with right Achilles tendonitis/cellulitis and was discharged on a one-week course of clindamycin. Twenty-five days later she was readmitted, complaining of pain and swelling in the same area, which this time presented as an abscess. Upon this admission, vancomycin and levofloxacin were initiated and incision and drainage (I & D) was performed. Cultures and sensitivities from I & D were significant for E. corrodens and A. odontolyticus, and treatment was changed to intravenous doxycycline 100 mg every 12 hours for 10 weeks. Oral doxycycline 100 mg every 12 hours was then used for 3 months, and treatment was successful. DISCUSSION: E. corrodens and A. odontolyticus are 2 slow-growing organisms that are part of the normal oropharyngeal flora. Extraoral infections due to either of these organisms may be difficult to treat and might need lengthier treatments than are necessary for most infections. First-line treatment for such infections is penicillins and cephalosporins; however, in a patient with penicillin allergy, treatment options become limited, as there is potential cross-reactivity with other agents. CONCLUSIONS: Patients with infections secondary to E. corrodens and/or A. odontolyticus in whom penicillin allergy is a concern can be treated effectively with doxycycline.