Mechanisms and management of inappropriate therapy in subcutaneous implantable cardioverter defibrillators.

Subcutaneous implantable cardioverter defibrillators (S-ICDs) provide reliable defibrillation and have enhanced supraventricular tachycardia discrimination and fewer infection rates compared with traditional transvenous systems. However, inappropriate shocks remain a frequent problem. Herein, we review the various mechanisms of these inappropriate therapies, some of which are unique to S-ICDs, and propose an algorithm for preventing recurrences. Proper screening of preimplants is essential to help minimize inappropriate therapies, but patients with hypertrophic cardiomyopathy, Brugada syndrome, and arrhythmogenic right ventricular cardiomyopathy are at particular risk and may require additional measures.

High impedance alert with safety switching: An unreported hazard of hybrid pacing systems.

Several Boston Scientific pacemaker models have a known issue with intermittent oversensing of the minute ventilation sensor when paired with non-Boston Scientific leads. Several of our patients with these hybrid systems have had transient out of range impedances and oversensing after safety switching which we suspected may be related. A retrospective analysis of 395 patients who had pacemakers implanted between 2015-2017 found that transient out of range impedances with safety switching was present in 9% of Boston Scientific pacemakers paired with Abbott or Medtronic leads compared with 0% in other device-lead combinations (P = 0.0089). We postulate that the root cause of the minute ventilation oversensing and transient high impedance issue is the same, a header-lead interaction from low-level incompatibility. Recognizing this issue is critical to prevent unnecessary lead revisions or extractions as it can be prevented with a simple reprogramming of lead pace/sense configuration.

T-wave oversensing is more dependent on ICD sensitivity algorithm than lead sensing configuration.

Modern implantable cardioverter defibrillators (ICD) employ dynamic sensing algorithms in order to protect against fine ventricular fibrillation without oversensing intrinsic activity. We present a patient with a Medtronic ICD who had inhibition of pacing and not inappropriate shocks due to T wave oversensing (TWOS) in both true bipolar (TB) and integrated bipolar (IB) sensing configurations. Rather than alternatives such as lead revision or programming to an unacceptably insensitive value, this was solved by exchanging for a Boston Scientific ICD. Although the literature suggests lead sensing configuration impacts TWOS, this case demonstrates ICD sensitivity algorithm may be a key determinant.

Dual AV Nodal Nonreentrant Tachycardia Resulting in Inappropriate ICD Therapy in a Patient with Cardiac Sarcoidosis.

Dual atrioventricular nodal nonreentrant tachycardia (DAVNNT) occurs due to concurrent antegrade conduction over fast and slow atrioventricular nodal pathways and is treated by slow pathway modification. We describe a unique case of a patient with cardiac sarcoidosis who received inappropriate ICD shocks for DAVNNT. Atrial and ventricular device electrograms satisfied both rate and V>A criteria for ventricular tachycardia. We postulate that alterations in refractoriness and conduction as is seen in cardiac sarcoidosis (CS) may have contributed to occurrence of DAVNNT.

Cognitive impairment, age, quality of life, and treatment strategy for atrial fibrillation in older adults: The SAGE-AF study.

BACKGROUND: Atrial fibrillation (AF) treatment includes anticoagulation for high stroke risk individuals and either rate or rhythm control strategies. We aimed to investigate the impact of age, geriatric factors, and medical comorbidities on choice of rhythm versus rate control strategy in older adults. METHODS: Patients with AF aged ≥65 years with CHA2 DS2 VASc score ≥2 and eligible for anticoagulation were recruited for the Systematic Assessment of Geriatric Elements-AF (SAGE-AF) prospective cohort study. An interview that included measures of HRQoL, cognitive function, vision, hearing, and frailty was performed. The association between these elements and AF treatment strategy was examined by multivariable logistic regression models. RESULTS: One thousand two hundred forty-four participants (mean age 76 years; 49% female; 85% non-Hispanic white) were enrolled. Rate and rhythm control were used in 534 and 710 participants, respectively. Compared to participants <75 years, those ≥75 were more likely to be treated with a rate control strategy (age 75-84 adjusted odds ratio [aOR] 1.37 [95% CI 0.99, 1.88]; age 85+ aOR = 2.05, 95% CI 1.30, 3.21). Those treated with a rate control strategy were more likely to have cognitive impairment (aOR = 1.50, 95% CI 1.13, 1.99), and peripheral vascular disease (PVD) (aOR = 1.82, 95% CI 1.22, 2.72) but less likely to have visual impairment (aOR 0.73 [0.55, 0.98]), congestive heart failure (CHF; aOR 0.68 [0.49, 0.94]) or receive anticoagulation (aOR 0.53, 95% CI 0.36, 0.78). CONCLUSION: Older age, cognitive impairment, and PVD were associated with use of rate control strategy. Visual impairment, CHF, and anticoagulation use were associated with a rhythm control strategy. There was no difference in HRQoL between the rate and rhythm control groups. This study suggests that certain geriatric elements may be associated with AF treatment strategies. Further study is needed to evaluate how these decisions affect outcomes.

Glucagon-like peptide-1 and myocardial protection: more than glycemic control.

Pharmacologic intervention for the failing heart has traditionally targeted neurohormonal activation and ventricular remodeling associated with cardiac dysfunction. Despite the multitude of agents available for the treatment of heart failure, it remains a highly prevalent clinical syndrome with substantial morbidity and mortality, necessitating alternative strategies of targeted management. One such area of interest is the ability to modulate myocardial glucose uptake and its impact on cardioprotection. Glucose-insulin-potassium (GIK) infusions have been studied for decades, with conflicting results regarding benefit in acute myocardial infarction. Based on the same concepts, glucagon-like peptide-1-[7-36] amide (GLP-1) has recently been demonstrated to be a more effective alternative in left ventricular (LV) systolic dysfunction. This paper provides a review on the current evidence supporting the use of GLP-1 in both animal models and humans with ischemic and nonischemic cardiomyopathy.

Differential effective refractory period as a useful marker of multiple accessory pathways.

Accessory pathway (AP) ablation failure may be related to multiple pathways which go unrecognized at the time of electrophysiology study. We present a patient who had two adjacent APs based on different preexcitation patterns as well as effective refractory periods (ERPs) which have not been previously described. Apart from leading to recurrent supraventricular tachycardia (SVT), multiple pathways are important to recognize as they more frequently predispose to malignant atrial arrhythmias.

Epidemiology of Atrial Fibrillation and Heart Failure: A Growing and Important Problem.

The global prevalence of atrial fibrillation (AF) and heart failure (HF) is rising. Population-based studies have observed that AF and HF often coexist, predispose to each other, and share risk factors. Age is the most potent risk factor for both AF and HF, but race plays an important role. Although AF and HF share common risk factors, adjusting for these risk factors does not explain the higher risk of AF patients developing HF and vice versa. Common pathophysiologic mechanisms may explain this linkage. The morbidity and mortality outcomes with combined AF and HF are substantial and warrant improved preventive strategies.

Management of Inflammatory Cardiac Masses.

Systemic rheumatologic and inflammatory disorders can affect almost any organ system, including the heart. The cardiac valves, conduction system, myocardium, endocardium, pericardium, and coronary arteries may be affected. Intracardiac masses may develop as part of the disease process or a consequence of their therapy, such as methotrexate-associated nodulosis. Optimal therapy in these cases is not known, since many patients are asymptomatic and the potential benefit of surgical excision must be weighed against its associated morbidity and mortality. Importantly, these inflammatory masses must be differentiated from thrombus, infection, and primary and metastatic tumors. We present three cases of inflammatory cardiac masses associated with rheumatoid arthritis and Wegener's granulomatosis, which were successfully treated conservatively, and propose a management algorithm. The benefits of such an approach must be individualized and weighed against the risks of systemic embolization, stroke and obstruction.

Diabetic cardiomyopathy.

Diabetes mellitus is well recognized as a potent and prevalent risk factor for accelerated atherosclerosis and ischemic heart disease. However, there is also evidence of cardiac dysfunction in diabetes in the absence of coronary atherosclerosis, termed diabetic cardiomyopathy. Changes in ventricular structure and left ventricular systolic and diastolic dysfunction have all been noted even in patients with well-controlled diabetes and without overt macrovascular complications. Insulin resistance, hyperglycemia, and increased free fatty acid metabolism promote coronary microvascular disease, sympathetic nervous system dysfunction, and ventricular remodeling, and may contribute to the altered cardiac phenotype seen in diabetes. In addition to standard therapy (angiotensin-converting enzyme inhibitors and beta-blockers), diabetic patients with left ventricular dysfunction are likely to benefit from targeted therapies to reduce insulin resistance and modulate substrate use.