Risk of occurrence of electromagnetic interference from the application of transcutaneous electrical nerve stimulation on the sensing function of implantable defibrillators.

BACKGROUND: Transcutaneous electrical nerve stimulation (TENS) is an established method for pain relief. But electrical TENS currents are also a source of electromagnetic interference (EMI). Thus, TENS is considered to be contraindicated in implantable cardioverter-defibrillator (ICD) patients. However, data might be outdated due to considerable advances in ICD and cardiac resynchronization therapy (CRT) filtering and noise protection algorithm technologies. The aim of this pilot safety study was to re-evaluate the safety of TENS in patients with modern ICDs. METHODS AND RESULTS: One hundred and seven patients equipped with 55 different models of ICD/CRT with defibrillators from 4 manufacturers underwent a standardized test protocol including TENS at the cervical spine and the thorax, at 2 stimulation modes-high-frequency TENS (80 Hz) and burst-mode TENS (2 Hz). Potential interference monitoring included continuous documentation of ECG Lead II, intracardiac electrograms and the marker channel. Electromagnetic interference was detected in 17 of 107 patients (15.9%). Most frequent were: interpretations as a premature ventricular beats (VS/S) in 15 patients (14%), noise reversion in 5 (4.6%) which resulted in temporary asynchronous pacing in 3 (2.8%), interpretation as ventricular tachycardia/ventricular fibrillation in 2 (1.9%), and premature atrial beat in 2 (1.9%) patients. Electromagnetic interference occurrence was influenced by position (chest, P < 0.01), higher current intensity (P < 0.01), and manufacturer (P = 0.012). CONCLUSION: Overall, only intermittent and minor EMI were detected. Prior to the use of TENS in patients with ICDs, they should undergo testing under the supervision of a cardiac device specialist.

The response to cardiac resynchronization therapy in LMNA cardiomyopathy.

AIMS: Cardiac implantable electronic device (CIED) therapy is fundamental to the management of LMNA cardiomyopathy due to the high frequency of atrioventricular block and ventricular tachyarrhythmias. We aimed to define the role of cardiac resynchronization therapy (CRT) in impacting heart failure in LMNA cardiomyopathy. METHODS AND RESULTS: From nine referral centres, LMNA cardiomyopathy patients who underwent CRT with available pre- and post-echocardiograms were identified retrospectively. Factors associated with CRT response were identified (defined as improvement in left ventricular ejection fraction [LVEF] ≥5% 6 months post-implant) and the associated impact on the primary outcome of death, implantation of a left ventricular assist device or cardiac transplantation was assessed. We identified 105 patients (mean age 51 ± 10 years) undergoing CRT, including 70 (67%) who underwent CRT as a CIED upgrade. The mean change in LVEF ∼6 months post-CRT was +4 ± 9%. A CRT response occurred in 40 (38%) patients and was associated with lower baseline LVEF or a high percentage of right ventricular pacing prior to CRT in patients with pre-existing CIED. In patients with a European Society of Cardiology class I guideline indication for CRT, response rates were 61%. A CRT response was evident at thresholds of LVEF ≤45% or percent pacing ≥50%. There was a 1.3 year estimated median difference in event-free survival in those who responded to CRT (p = 0.04). CONCLUSION: Systolic function improves in patients with LMNA cardiomyopathy who undergo CRT, especially with strong guideline indications for implantation. Post-CRT improvements in LVEF are associated with survival benefits in this population with otherwise limited options.

Hyperkalaemia in Heart Failure.

Hyperkalaemia has become an increasingly prevalent finding in patients with heart failure (HF), especially with renin-angiotensin-aldosterone system (RAAS) inhibitors and angiotensin-neprilysin inhibitors being the cornerstone of medical therapy. Patients living with HF often have other comorbidities, such as diabetes and chronic kidney disease, which predispose to hyperkalaemia. Until now, we have not had any reliable or tolerable therapies for the treatment of hyperkalaemia to facilitate implementation or achievement of target doses of RAAS inhibition. Patiromer sorbitex calcium and sodium zirconium cyclosilicate are two novel potassium-binding resins that have shown promise in the management of patients predisposed to developing recurrent hyperkalaemia, and their use may allow for further optimisation of guideline directed medical therapy.

Evidence-Based Management of Acute Heart Failure.

Acute heart failure (AHF) is a complex, heterogeneous, clinical syndrome with high morbidity and mortality, incurring significant health care costs. Patients transition from home to the emergency department, the hospital, and home again and require decisions surrounding diagnosis, treatment, and prognosis at each step of the way. The purpose of this review is to examine the epidemiology, etiology, and classifications of AHF and specifically focus on practical information relevant to the clinician. We examine the mechanisms of decompensation relevant to clinical presentations-including precipitating factors, neuroendocrine interactions, and inflammation-along with how consideration of these factors may help select therapies for an individual patient. The prevalence and significance of end-organ manifestations such as renal, gastrointestinal, respiratory, and neurologic manifestations are discussed. We also highlight how the development of renal dysfunction relates to the choice of a variety of diuretics that may be useful in specific circumstances and review guideline-directed medical therapy. We discuss the practical use (and pitfalls) of a variety of evidence-based clinical scoring criteria available to risk stratify patients with AHF. Finally, evidence-based management of AHF is discussed, including both pharmacologic and nonpharmacologic therapies, including the lack of evidence for using old and new vasodilators and the recent evidence regarding initiation of newer therapies in hospital. Overall, we suggest that clinicians consider implementing the newer data in AHF and subject existing practice patterns and treatments to the same rigour as new therapies.

Ventricular tachycardia in cardiolaminopathy: Characteristics and considerations for device programming.

BACKGROUND: Mutations in LMNA cause an arrhythmogenic cardiomyopathy (cardiolaminopathy) with high risk of ventricular tachycardia (VT). The natural history of VT among patients with cardiolaminopathy is incompletely understood. OBJECTIVE: The purpose of this study was to determine the longitudinal burden and progression of VT, including change in tachycardia cycle length (TCL), response to antitachycardia pacing (ATP), and prognostic significance of high-burden VT (>5 episodes of VT at any device interrogation) in cardiolaminopathy patients. METHODS: Patients with cardiolaminopathy and an implantable cardioverter-defibrillator (ICD) were identified from a single-center database. Serial device interrogations and medical records were used to collect data on VT burden, TCL, and response to ATP. RESULTS: Cardiolaminopathy patients with primary (n = 27) or secondary prevention (n = 16) ICDs were followed for 2 years (interquartile range [IQR] 1-5). VT burden was substantially higher in patients receiving secondary prevention ICDs (28 ± 40.9 vs 3.6 ± 7.3 episodes per 100 patient-years; P <.001). ATP was highly effective (94%) at terminating VT except for short TCL (<250 ms), for which ATP failed in 60%. Among patients with recurrent VT, TCL increased by 112 ± 93.6 ms during follow-up. Inappropriate shocks were rare (0.4% of all therapies). Median time to transplantation, ventricular assist device, or death was 18 months (IQR 0.7-27.1) in patients with high-burden VT. CONCLUSION: In patients with cardiolaminopathy, VT is recurrent and highly responsive to ATP, which supports the use of transvenous ICDs iteratively programmed to manage VT of various TCLs. Onset of high-burden VT indicates poor prognosis and should warrant referral to a heart failure specialist.

Evolving trends in mechanical circulatory support: Clinical development of a fully magnetically levitated durable ventricular assist device.

Early generation left ventricular assist devices (LVAD) for treatment of refractory heart failure attempted to mimic the pulsatility of a native heart and were bulky and less durable due to valves within the inflow and outflow pathways. The next disruption came with the introduction of continuous flow pumps characterized by a low-pulse pressure circulation. Since the mechanism of action did not involve displacement of blood, these pumps were much smaller and less noisy in part due to fewer moving parts. Such devices include the HeartMate II axial-flow pathway pump which is implanted thoraco-abdominally and the HVAD, a centrifugal-flow pathway pump which is smaller and is implanted entirely within the thoracic cavity and uses a combination of hydrodynamic and magnetic levitation of the internal rotor. These pumps improved survival compared with the early generation LVADs and in a trial, the HVAD demonstrated non-inferiority compared with the HeartMate II but with an increase in ischemic and hemorrhagic strokes. The HeartMate 3 LVAD is an intrapericardial centrifugal-flow pathway pump with a full magnetically levitated, frictionless rotor with a fixed intrinsic pulse. In a randomized trial, the HeartMate 3 "hybrid" pump was associated with near-elimination of pump thrombosis, a reduction in strokes of any type or severity and lower mucosal bleeding rates. Despite improvements in hemocompatibility, right heart failure and infections contribute to significant morbidity, and devices designed to be internally contained with a wireless power source and physiological flow characteristics are still required despite great strides in the field.

Hyperkalemia in heart failure.

PURPOSE OF REVIEW: Hyperkalemia is increasingly prevalent in the heart failure population as more people live with heart failure and comorbid conditions such as diabetes and chronic kidney disease. Furthermore, renin-angiotensin-aldosterone (RAAS) inhibitors are a key component of clinical therapy in these populations. Until now, we have not had any reliable or tolerable therapies for treatment of hyperkalemia resulting in inability to implement or achieve target doses of RAAS inhibition. This review will focus on two new therapies for hyperkalemia: patiromer and sodium zirconium cyclosilicate (SZC). RECENT FINDINGS: Patiromer and SZC have been studied in heart failure and both agents have demonstrated the ability to maintain normokalemia for extended periods of time with improved side effect profiles than existing potassium binders such as sodium polystyrene sulfate, though no direct comparisons have occurred. SZC has also shown promise in the treatment of acute hyperkalemia with its quick onset of action. SUMMARY: Patiromer and SZC will be useful adjuncts in the clinical care of heart failure patients with hyperkalemia. These agents will allow clinicians to maintain patients on RAAS inhibitors and uptitrate their guideline directed medical therapy to target doses without the additional concern for recurrent hyperkalemia and its untoward effects.

Modifiable Risk Factors in Atrial Fibrillation: The Role of Alcohol, Obesity, and Sleep Apnea.

Atrial fibrillation (AF) is a common arrhythmia affecting a growing number of Canadians. Traditional risk factors, such as hypertension, diabetes, and valvular disease, are often present in older patients with AF. Modifiable risk factors should also be sought in patients presenting with new-onset AF. Obesity is a rapidly growing epidemic in Canada. Emerging evidence is linking obesity and the often coexistent obstructive sleep apnea with an increased incidence of AF. Alcohol intake can also predispose to the development of AF. The purpose of this article is to review recent evidence looking at these modifiable risk factors and how intervention can mitigate these increased risks.

Atrial fibrillation management: evaluating rate vs rhythm control.

Atrial fibrillation (AF) is an increasing global issue leading to increased hospitalizations, adverse health related events and mortality. This review focuses on the management of atrial fibrillation, in particular in the past decade, comparing two major strategies, rate or rhythm control. We evaluate the evidence for each strategy, pharmacological options and the increasing utilization of invasive techniques, in particular catheter ablation and use of implantable cardiac pacing devices. Pharmacological comparative trials evaluating both strategies have shown rate control being non-inferior to rhythm control for clinical outcomes of mortality and other cardiovascular events (including stroke). Catheter ablation techniques, involving radiofrequency ablation and recently cryoablation, have shown promising results in particular with paroxysmal AF. However, persistent AF provides ongoing challenges and will be a particular focus of continued research.

Screening, detecting and enhancing the yield of previously undiagnosed hepatitis B and C in patients with acute medical admissions to hospital: a pilot project undertaken at the Vancouver General Hospital.

BACKGROUND: Hepatitis B virus (HBV) and hepatitis C virus (HCV) represent an increasing health burden and morbidity in Canada. Viral hepatitis, specifically HCV, has high prevalence among persons born between 1945 and 1965, with 45% to 85% of infected adults asymptomatic and unaware of their infection. Screening has been shown to be cost effective in the detection and treatment of viral hepatitis. OBJECTIVE: To quantify incidence and identify undocumented HBV and HCV infection in hospitalized patients at a single centre with secondary analysis of risk factors as part of a quality improvement initiative. METHODS: A one-time antibody test was conducted in patients admitted to the acute medicine and gastroenterology services. RESULTS: Over a 12-week period, hospital screening for HBV and HCV was performed in 37.3% of 995 admitted patients. There was identification of 15 previously undiagnosed cases of HCV (4%) and 36 undocumented cases of occult (ie, antihepatitis B core antigen seropositive) or active (ie, hepatitis B surface antigen seropositive) HBV (9.7%). Among patients with positive screens, 60% of seropositive HCV patients had no identifiable risk factors. CONCLUSIONS: The prevalence of HBV and HCV infection among hospitalized patients in Vancouver was higher than that of the general population. Risk factors for contraction are often not identified. These results can be used as part of an ongoing discussion regarding a 'seek and treat' approach to the detection and treatment of chronic blood-borne viral illnesses.

Impact of QRS morphology and duration on outcomes after cardiac resynchronization therapy: Results from the Resynchronization-Defibrillation for Ambulatory Heart Failure Trial (RAFT).

BACKGROUND: The impact of QRS morphology and duration on the effectiveness of cardiac resynchronization therapy (CRT) has been usually assessed separately. The interaction between these 2 simple ECG parameters and their effect on CRT has not been systematically assessed in a large-scale clinical trial. METHODS AND RESULTS: The Resynchronization-Defibrillation for Ambulatory Heart Failure Trial showed that implantable cardioverter defibrillator-CRT was associated with a significant reduction in the primary end point of all-cause mortality or heart failure hospitalization. For this substudy, we excluded patients in atrial fibrillation and those with a previous pacemaker. All baseline ECGs were reviewed by a panel of 3 experienced electrocardiographers. A total of 1483 patients were included in this study. Of these, 1175 had left bundle-branch block (LBBB) and 308 had non-LBBB. In patients with LBBB receiving implantable cardioverter defibrillator-CRT, there was a reduction in the primary outcome and in each individual component of the primary outcome. Furthermore, there was continuous relationship between QRS duration and extent of benefit. In patients with non-LBBB and QRS ≥160 ms, the hazard ratio for the primary outcome was 0.52 (0.29-0.96; P=0.033); in patients with QRS <160 ms, the hazard ratio was 1.38 (0.88-2.14; P=0.155). CONCLUSIONS: In patients with LBBB, there was a continuous relationship between broader QRS and greater benefit from implantable cardioverter defibrillator-CRT. However, our data do not support the use of implantable cardioverter defibrillator-CRT in patients with non-LBBB, especially when the QRS duration is <160 ms. There may be some delayed benefit when the QRS is ≥160 ms, but this needs further investigation. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00251251.

Antimicrobial therapy in patients with acute variceal hemorrhage.

BACKGROUND: Acute variceal hemorrhage is a serious complication of liver disease and hospital outcome is closely related to infection. Patients with cirrhosis are at greater risk for developing bacterial infection, which is associated with failure to control bleeding and higher rates of hospital mortality. Many clinical practice guidelines endorse antimicrobial prophylaxis as standard of care for cirrhotic patients. OBJECTIVE: The present study was performed to characterize the use of antimicrobial therapy for patients hospitalized with acute variceal hemorrhage. METHODS: Medical records of 98 patients hospitalized with suspected variceal hemorrhage were retrospectively reviewed. RESULTS: One-half of the patients received antimicrobials at any time during their hospital admission, and in very few (24%) could prescribed therapy be considered prophylactic. Seventy-seven per cent of patients undergoing endoscopy did not receive an antimicrobial within 24 h of the procedure. Those who received antimicrobial therapy had more severe liver disease (model for end-stage liver disease scores of 19.5 +/- 10 versus 12.9 +/- 8, P< 0.05; Child-Pugh class C 78% versus 65%, not significant) and worse in-hospital outcome (length of stay 17 versus 6.5 days, P<0.05; mortality 15 versus two, P< 0.05). Cephalosporins were the most widely prescribed agents (45%), followed by fluoroquinolone (40%). Regimens ranged in length from single-dose administration to two weeks. CONCLUSIONS: Patients with liver disease admitted with variceal hemorrhage were often not prescribed antimicrobial therapy to reduce the risk of bacterial infection. These results imply that published practice guidelines are not being consistently observed. A large, well-designed study with mortality outcome may be required for clinical guidelines to be successfully implemented in practice.