Single- Versus Dual-Chamber Implantable Cardioverter-Defibrillator for Primary Prevention of Sudden Cardiac Death in the United States

Background Routine addition of an atrial lead during an implantable cardioverter-defibrillator (ICD) implantation for primary prevention of sudden cardiac death, in patients without pacing indications, was not shown beneficial in contemporary studies. We aimed to investigate the use and safety of single- versus dual-chamber ICD implantations in these patients. Methods and Results Using the National Inpatient Sample database, we identified patients with no pacing indications who underwent primary-prevention ICD implantation in the United States between 2015 and 2019. Sociodemographic and clinical characteristics, as well as in-hospital complications, were analyzed. Multivariable logistic regression was used to identify predictors of in-hospital complications. An estimated total of 15 940 patients, underwent ICD implantation for primary prevention of sudden cardiac death during the study period, 8860 (55.6%) received a dual-chamber ICD. The mean age was 64 years, and 66% were men. In-hospital complication rates in the dual-chamber ICD and single-chamber ICD group were 12.8% and 10.7%, respectively (P<0.001), driven by increased rates of pneumothorax/hemothorax (4.6% versus 3.4%; P<0.001) and lead dislodgement (3.6% versus 2.3%; P<0.001) in the dual-chamber ICD group. Multivariable analyses confirmed atrial lead addition as an independent predictor for "any complications" (odds ratio [OR], 1.1 [95% CI, 1.0-1.2]), for pneumo/hemothorax (odds ratio, 1.1 [95% CI, 1.0-1.4]), and for lead dislodgement (odds ratio, 1.3 [95% CI, 1.1-1.6]). Conclusions Despite lack of evidence for clinical benefit, dual-chamber ICDs are implanted for primary prevention of sudden cardiac death in a majority of patients who do not have pacing indication. This practice is associated with increased risk of periprocedural complications. Avoidance of routine implantation of atrial leads will likely improve safety outcomes.

A case of complete heart block in a COVID-19 infected patient

In the midst of the COVID-19 pandemic, we herein report the case of an elderly female with multiple comorbidities coming with typical symptoms of the viral infection in addition to the unusual presentation of bradycardia due to complete heart block requiring pacemaker placement. This may be a rare complication of the disease but one has to keep a high index of suspicion since this virus has an ability to affect multiple organ systems with many ways yet to be uncovered. .

Interdisciplinary strategies for arrhythmia program development: measuring quality, performance, and outcomes

Evidence-based medicine has provided the foundation for refinement of the guideline development process and the emergence of the disciplines of measuring quality, performance, and outcomes. With implementation of electronic medical records as part of healthcare reform, multiple aspects of these disciplines will be incorporated into clinical cardiac electrophysiology. Performance measures and quality metrics will assume an influential role in the management of patients with heart rhythm disturbances in the near future.

Effectiveness of automated external defibrillators in high schools in greater Boston

A program using a strategy of donating a single automatic external defibrillator to 35 schools in the Boston area resulted in compliance with American Heart Association guidelines on automatic external defibrillator placement and training and 2 successful resuscitations from sudden cardiac arrest. Participating schools indicated a high degree of satisfaction with the program.

Extraction of buried P waves from printed electrocardiograms

BACKGROUND

Morphologic identification of ectopic P-waves from surface ECGs can be challenging, particularly when the P-wave is buried in the QRST wave complex. Because ECGs are often available on paper and not digitally, we developed a method of subtracting the T-wave from the buried P-wave complex on paper ECGs.

METHODS

To validate our system, an atrial extrastimulus was introduced during and following the T-wave. The ECGs were scanned and then transformed from an image format to a digital format. A computer algorithm digitally subtracted a QRST with no buried P-wave from one with a buried P-wave, thus resulting in an extracted P-wave. The extracted P-waves were compared to the nonburied P-wave by determining correlation coefficients and by visual grading by two independent reviewers.

RESULTS

Visual grading comparing the buried P-wave with the exposed paced P-wave was 94%. The median correlation coefficient was 85%.

CONCLUSIONS

An ectopic atrial P-wave obscured by a coincident QRST wave complex can be accurately derived from printed ECG using this PC-based system. Addition of this technique to the existing methods may aid in the localization and ablation of ectopic atrial foci.

Device trials in heart failure: a focused summary

Despite considerable progress in heart failure management with pharmacologic agents, measures to bring about significant improvements in morbidity and mortality are still needed. Cardiac resynchronization therapy (CRT) is a means to enhance myocardial function by stimulating the failing left ventricle at or near the time of right ventricular activation to synchronize ventricular depolarization. Current data from randomized, controlled trials suggest that CRT benefits patients with moderate to severe heart failure and have shown that this therapy significantly reduces mortality and hospital admissions in this group. In addition to CRT, implantable cardioverter-defibrillators have been evaluated in heart failure patients with significantly reduced left ventricular function and have been shown to reduce mortality from sudden cardiac death. This article summarizes recent device trials and discusses how best to apply their results to clinical practice.

ECG Findings in Active Patients: Differentiating the Benign From the Serious

ECGs and cardiac rhythms of normal athletes can vary widely. The heightened vagal tone from athletic conditioning can result in variant ECG findings that may mimic serious disorders. ECG patterns of long-QT syndrome, arrhythmogenic right ventricular dysplasia, Wolff-Parkinson-White syndrome, and hypertrophic cardiomyopathy signal the need for further evaluation, therapy, and possible participation restriction. Radiofrequency ablation may be appropriate when symptomatic supraventricular arrhythmias or Wolff-Parkinson-White syndrome is present. Further research is needed to effectively distinguish normal ECG changes in the athlete from changes that underlie cardiac disease. Improvements in identifying athletes at risk of serious or life-threatening arrhythmias are also needed.

Analysis of intracardiac electrograms showing monomorphic ventricular tachycardia in patients with implantable cardioverter-defibrillators

Ventricular tachycardia (VT) initiation and its relation to various clinical factors was studied by reviewing intracardiac electrograms from patients with implantable cardioverter-defibrillators. Events were divided into (1) sudden onset without preceding ventricular premature complexes (VPCs), (2) extrasystolic onset with VPCs, or (3) paced, depending on the type and morphology of the last 5 beats before initiation of VT. Prematurity index, sinus rate, cycle length, and presence of short-long-short sequence for each episode was noted. A total of 268 episodes of VT among 52 patients were analyzed. Extrasystolic initiation was the most frequent pattern (177; 66%) followed by sudden onset (75; 28%) and paced (16; 6%). Among extrasystolic onset, 99 episodes (56%) were due to multiple VPCs and 149 episodes (84%) had different VPC morphology than the subsequent VT. Among pacing-induced VT, 13 of 16 episodes were due to inappropriate pacing due to undersensing of prior R waves. Sudden-onset episodes were slower (mean cycle length 383+/-97 ms) than extrasystolic (mean cycle length 336+/-88 ms, p = 0.002) and paced (mean cycle length 313+/-85 ms, p = 0.01) onset. Patients in the sudden-onset group had better left ventricular ejection fraction (33+/-15%) than the extrasystolic (29+/-11%, p<0.001) and paced (28+/-14%, p<0.01) groups. Extrasystolic onset with multiple, late coupled VPCs was the most common pattern of VT initiation and was associated with lower ejection fraction. Sudden-onset initiation was more common with better preserved systolic function.

Combined radiofrequency ablation-cooling catheter for reversible cryothermal mapping and ablation

Reversible cryothermal mapping of cardiac arrhythmias has been performed intraoperatively. However, a steerable cooling catheter for reversible mapping has not yet been developed. We therefore developed and tested a cooling system consisting of a -15 degrees C hypertonic saline reservoir and a 7F steerable catheter also capable of radiofrequency (RF) ablation. Using excised ovine hearts placed in a 37 degrees C circulating saline bath, we measured the temperatures at depths of 0 mm, 1 mm, and 2 mm. The temperature after 90 seconds of cooling was 16.5 +/- 2.1 degrees C at 0 mm compared to 23.9 +/- 4.1 degrees C at 1 mm and 31.1 +/- 3.9 degrees C at 2 mm depth (p < 0.01). These data suggest that a 7F steerable combined RF ablation-cooling catheter may achieve temperatures suitable for mapping arrhythmias such as atrial tachycardias and right ventricular outflow tract tachycardias. Further enhancements to achieve lower temperatures at depth may be needed to reversibly map other arrhythmias such as left ventricular tachycardias.

Atrioventricular junctional ablation and modification for atrial fibrillation

RF catheter ablation is a safe and extremely effective method of achieving complete A-V block in patients with difficult-to-control ventricular rates in atrial fibrillation. In selected patients, A-V junction ablation may improve exercise capacity and functional status while reducing the need for emergency care and hospitalization. Prospective, randomized studies are needed, however, to compare A-V junction ablation as a management strategy to pharmacologic therapy to control ventricular rate or to maintain sinus rhythm. Similarly, additional data are needed to assess methods of achieving A-V junction modification with the lowest risk for A-V block.

Strategies for managing atrial fibrillation

The limitations of current therapies for atrial fibrillation are forcing a rethinking of how they should be used. Questions are being raised about the use of antiarrhythmic drugs, and new nonpharmacologic procedures are promising alternatives. Most patients with atrial fibrillation still require warfarin therapy, but some low-risk patients can forego it. Sinus rhythm spontaneously returns within the first 24 hours in almost half of cases of new atrial fibrillation. Patients with hemodynamic instability due to new-onset atrial fibrillation should proceed directly to electrical cardioversion. Warfarin therapy to maintain an International Normalized Ratio (INR) of 2.0 to 3.0 is currently recommended for all patients with atrial fibrillation with no contraindications to it, except for patients younger than 60 years with lone atrial fibrillation, in whom the risk of stroke is low. Certain antiarrhythmic drugs should be avoided in patients with congestive heart failure, in whom the risks may exceed the benefits. The maze procedure is emerging as an option to restore and maintain sinus rhythm. Radiofrequency atrioventricular node ablation and modification hold promise as options to control the ventricular rate without drugs.

A new platinum balloon-expandable stent (Angiostent) mounted on a high pressure balloon: acute and late results in an atherogenic swine model

BACKGROUND

Randomized studies have proven the efficacy and safety of stent placement to treat de novo coronary stenosis. However, the poor radio-opacity and the use of an additional high-pressure balloon to fully expand the stent are the major limitations of the currently clinically-approved stents.

OBJECTIVE

We evaluated the safety, efficacy, angiographic and histologic effect of a new platinum balloon expandable stent mounted on a high-pressure balloon in Yucatan miniature swine fed high cholesterol diet.

METHODS

Fifteen Angiostents (NuMED, Inc., Hopkinton, NY and Angiodynamics, Glens Falls, NY) (coronary stent was 3, 3.5, or 4 mm in diameter and 12 mm long; renal and carotid stents were 5 mm in diameter and 13 mm long) mounted on a high-pressure balloon were placed percutaneously in blood vessels of 10 pigs [5 in circumflex (CX), 2 in left anterior descending (LAD), 5 in renal and 3 in carotid arteries]. The stent was 10-20% larger than the native vessel diameter. All animals received 5000 I.U. of heparin during the procedure and were maintained on 325 mg aspirin daily. Follow-up angiography and histology in the animals was performed at 2, 4, 12, 20, 26 and 52 weeks.

RESULTS

The stents were easily visualized with fluoroscopy and placed in all animals without episodes of balloon rupture or embolization. There was no episode of acute thrombosis. Follow-up angiography in the animals revealed patency of all renal and carotid stents, however, 2/7 coronary stents in the animals revealed angiographic lumen narrowing (> 20%) at 20 and 52 weeks. Histologic examination revealed neointimal formation at the stent site with an average neointimal thickness ranging from 325-650 microns.

CONCLUSION

This stent was safe in this animal model, easily deployed, had excellent radio-opacity and with good short-term patency without anticoagulation. Clinical trials and experience is underway.