Hans Moore

Improving SVT Discrimination in Single‐Chamber ICDs: A New Electrogram Morphology‐Based Algorithm

Introduction: Wide‐spread adoption of ICD therapy has focused efforts on improving the quality of life for patients by reducing “inappropriate” shock therapies. To this end, distinguishing supraventricular tachycardia from ventricular tachycardia remains a major challenge for ICDs. More sophisticated discrimination algorithms based on ventricular electrogram morphology have been made practicable by the increased computational ability of modern ICDs.

Monophasic Action Potential Recordings in Humans

Bridging basic and clinical electrophysiology has been facilitated by monophasic action potential recordings. The electrocardiogram is a useful clinical approach in detecting abnormal repolarization, but falls short in depicting local repolarization details. The MAP waveform is a reflection of local transmembrane action potentials. We hope to convey a basic understanding of monophasic action potential recording and highlight the clinical utility in both ventricular and atrial arrhythmias.

Cardiorespiratory Fitness and Incidence of Major Adverse Cardiovascular Events in US Veterans: A Cohort Study.

Objective: To assess the association between exercise capacity and the risk of major adverse cardiovascular events (MACEs). Patients and Methods: A symptom‐limited exercise tolerance test was performed to assess exercise capacity in 20,590 US veterans (12,975 blacks and 7615 whites; mean ± SD age, 58.2±11.0 years) from the Veterans Affairs medical centers in Washington, District of Columbia, and Palo Alto, California. None had a history of MACE or evidence of ischemia at the time of or before their exercise tolerance test. We established quintiles of cardiorespiratory fitness (CRF) categories based on age‐specific peak metabolic equivalents (METs) achieved. We also defined the age‐specific MET level associated with no risk for MACE (hazard ratio [HR], 1.0) and formed 4 additional CRF categories based on METs achieved below (least fit and low fit) and above (moderately fit and highly fit) that level. Multivariate Cox models were used to estimate HR and 95% CIs for mortality across fitness categories. Results: During follow‐up (median, 11.3 years; range, 0.3–33.0 years), 2846 individuals experienced MACEs. The CRF‐MACE association was inverse and graded. The risk for MACE declined precipitously for those with a CRF level of 6.0 METs or higher. When considering CFR categories based on the age‐specific MET threshold, the risk increased for those in the 2 CFR categories below that threshold (HR, 1.95; 95% CI, 1.73–2.21 and HR, 1.41; 95% CI, 1.27–1.56 for the least‐fit and low‐fit individuals, respectively) and decreased for those above it (HR, 0.77; 95% CI, 0.68–0.87 and HR, 0.57; 95% CI, 0.48–0.67 for moderately fit and highly fit, respectively). Conclusion: Increased CRF is inversely and independently associated with the risk for MACE. When an age‐specific MET threshold was defined, the risk for MACE increased significantly for those below that threshold and decreased for those above it (P<.001).

Exercise Capacity and Atrial Fibrillation Risk in Veterans: A Cohort Study.

OBJECTIVE To assess the association between exercise capacity and the risk of developing atrial fibrillation (AF). PATIENTS AND METHODS A symptom-limited exercise tolerance test was conducted to assess exercise capacity in 5962 veterans (mean age, 56.8±11.0 years) from the Veterans Affairs Medical Center, Washington, DC. None had evidence of AF or ischemia at the time of or before undergoing their exercise tolerance test. We established 4 fitness categories based on age-stratified quartiles of peak metabolic equivalent task (MET) achieved: least fit (4.9±1.10 METs; n=1446); moderately fit (6.7±1.0 METs; n=1490); fit (7.9±1.0 METs; n=1585), and highly fit (9.3±1.2 METs; n=1441). Multivariable Cox proportional hazards regression models were used to compare the AF-exercise capacity association between fitness categories. RESULTS During a median follow-up period of 8.3 years, 722 (12.1%) individuals developed AF (14.5 per 1000 person-years; 95% CI, 13.9-15.9 per 1000 person-years). Exercise capacity was inversely related to AF incidence. The risk was 21% lower (hazard ratio, 0.79; 95% CI, 0.76-0.82) for each 1-MET increase in exercise capacity. Compared with the least fit individuals, hazard ratios were 0.80 (95% CI, 0.67-0.97) for moderately fit individuals, 0.55 (95% CI, 0.45-0.68) for fit individuals, and 0.37 (95% CI, 0.29-0.47) for highly fit individuals. Similar trends were observed in those younger than 65 years and those 65 years or older. CONCLUSION Increased fitness is inversely and independently associated with the reduced risk of developing AF. The decrease in risk was graded and precipitous with only modest increases in exercise capacity. These findings counter previous suggestions that even moderate increases in physical activity, as recommended by national and international guidelines, increase the risk of AF, with marked protection against AF noted with increasing levels of fitness.

Characteristics and Incidence of Chronic Illness in Community-Dwelling Predominantly Male U.S. Veteran Centenarians

To assess the incidence of chronic illness and its effect on veteran centenarians.

A Patch in the Pectoral Position Lowers Defibrillation Threshold

Implantable pacemaker cardioverter defibrillators are now available with biphasic waveforms, which have been shown to markedly improve defibrillation thresholds (DFTs). However, in a number of patients the DFT remains high. Also, DFT may increase after implantation, especially if antiarrhythmic drugs are added. We report on the use of a subcutaneous patch in the pectoral position in 15 patients receiving a transvenous defibrillator as a method of easily reducing the DFT. A 660‐mm2 patch electrode was placed beneath the generator in a pocket created on the pectoral fascia. The energy required for defibrillation was lowered by 56% on average, and the system impedance was lowered by a mean of 25%. This maneuver allowed all patients to undergo a successful implant with adequate safety margin.

A 108-Year-Old Centenarian Survivor of Acute Decompensated Heart Failure and Acute Kidney Injury

To the Editor: Heart failure in centenarians is an especially challenging syndrome, as these patients frequently suffer from comorbidities and functional impairments. Age-related physiological changes can also affect pharmacokinetics and pharmacodynamics and may influence patient response tomedication. Unfortunately, in this growing segment of the nation’s population, evidence-based treatment guidelines are lacking. We report our experience treating a 108-year-old centenarian with acute decompensated heart failure and acute kidney injury. The goals of care, as articulated by the patient, were to reduce disease burden and to improve her quality of life and survival. These goals were accomplished through an involved interdisciplinary treatment team, closely monitored conservative medical care, and the cooperation of our resilient patient. Heart failure (HF) is a worldwide complex and chronic clinical syndrome that increaseswith age.1 The changing demographics of the rapidly growing segment of the oldest old seem to be contributing to the increasing prevalence of HF with an age-adjusted mortality that appears to be increasing as well.2 The lifetime risk for HF in octogenarians is estimated to be 20%.3 For persons residing in skilled nursing facilities (SNFs) in the United States, HF is commonwith an estimated prevalence of 25% and 1-year mortality exceeding 50%.4 Despite the high prevalence of HF in the oldest old, there is a lack of large randomized clinical trials for octogenarians, nonagenarians, centenarians, or patients residing in SNFs. We will present the case of our patient and review the literature regarding medical management of elderly patients with HF accompanied by kidney injury.

How Should Implantable Cardioverter-Defibrillator Lead Failures be Managed and What is the Role of Lead Extraction?

Despite remarkable advances in design, implantable cardioverter-defibrillator (ICD) leads remain the component most susceptible to failure, which often leads to substantial adverse clinical outcomes. This article focuses on management strategies when ICD lead systems fail. Two cases involving management decisions for ICD lead failures are presented and discussed. One involves a common mode of presentation, inappropriate shocks. The second involves an alert in a patient with a complex system and multiple comorbidities. Although a systematic approach is outlined, management decisions must be balanced by a risk-and-benefit assessment of the individual patient.

Association between lifetime risk of atrial fibrillation and mortality in the oldest old

Age is the strongest predictor of atrial fibrillation (AF), yet little is known about AF incidence in the oldest old.

A Case of Influenza type A Myocarditis that presents with ST elevation MI, Cardiogenic Shock, Acute Renal Failure, and Rhabdomyolysis and with rapid recovery after Treatment with Oseltamivir and Intra-Aortic Balloon Pump Support

We present a 59-year-old black male with history of type-1 diabetes and alcohol abuse. Patient became critically ill after a 5-day period of burning throat discomfort. On arrival patient was lethargic, in cardiogenic shock with a blood pressure of 81/47mmHg. Immediate diagnoses included diabetic ketoacidosis, acute renal failure, and possible septic shock. He was intubated, resuscitated with intravenous fluids, maintained on three inotropic agents, and given empiric wide spectrum antibiotics. An ECG showed a new ST elevation MI and an echocardiogram showed severe LV dysfunction. Cardiac catheterization showed clean coronaries. With appropriate treatment patient recovered 10days later.