Efficacy and Safety of Appropriate Shocks and Antitachycardia Pacing in Transvenous and Subcutaneous Implantable Defibrillators: Analysis of All Appropriate Therapy in the PRAETORIAN Trial.

BACKGROUND: The PRAETORIAN trial (A Prospective, Randomized Comparison of Subcutaneous and Transvenous Implantable Cardioverter Defibrillator Therapy) showed noninferiority of subcutaneous implantable cardioverter defibrillator (S-ICD) compared with transvenous implantable cardioverter defibrillator (TV-ICD) with regard to inappropriate shocks and complications. In contrast to TV-ICD, S-ICD cannot provide antitachycardia pacing for monomorphic ventricular tachycardia. This prespecified secondary analysis evaluates appropriate therapy and whether antitachycardia pacing reduces the number of appropriate shocks. METHODS: The PRAETORIAN trial was an international, investigator-initiated randomized trial that included patients with an indication for implantable cardioverter defibrillator (ICD) therapy. Patients with previous ventricular tachycardia <170 bpm or refractory recurrent monomorphic ventricular tachycardia were excluded. In 39 centers, 849 patients were randomized to receive an S-ICD (n=426) or TV-ICD (n=423) and were followed for a median of 49.1 months. ICD programming was mandated by protocol. Appropriate ICD therapy was defined as therapy for ventricular arrhythmias. Arrhythmias were classified as discrete episodes and storm episodes (≥3 episodes within 24 hours). Analyses were performed in the modified intention-to-treat population. RESULTS: In the S-ICD group, 86 of 426 patients received appropriate therapy, versus 78 of 423 patients in the TV-ICD group, during a median follow-up of 52 months (48-month Kaplan-Meier estimates 19.4% and 17.5%; P=0.45). In the S-ICD group, 83 patients received at least 1 shock, versus 57 patients in the TV-ICD group (48-month Kaplan-Meier estimates 19.2% and 11.5%; P=0.02). Patients in the S-ICD group had a total of 254 shocks, compared with 228 shocks in the TV-ICD group (P=0.68). First shock efficacy was 93.8% in the S-ICD group and 91.6% in the TV-ICD group (P=0.40). The first antitachycardia pacing attempt successfully terminated 46% of all monomorphic ventricular tachycardias, but accelerated the arrhythmia in 9.4%. Ten patients with S-ICD experienced 13 electrical storms, versus 18 patients with TV-ICD with 19 electrical storms. Patients with appropriate therapy had an almost 2-fold increased relative risk of electrical storms in the TV-ICD group compared with the S-ICD group (P=0.05). CONCLUSIONS: In this trial, no difference was observed in shock efficacy of S-ICD compared with TV-ICD. Although patients in the S-ICD group were more likely to receive an ICD shock, the total number of appropriate shocks was not different between the 2 groups. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT01296022.

Percutaneous occlusion balloon as a bridge to surgery in a swine model of superior vena cava perforation.

BACKGROUND: Superior vena cava (SVC) perforation is a rare but potentially fatal complication of transvenous lead removal. OBJECTIVE: The aim of this study was to evaluate the feasibility of hemodynamic stabilization using an occlusion balloon during SVC tear in a porcine model. METHODS: A surgically induced SVC perforation was created in Yorkshire cross swine (n = 7). Three animals were used to develop and test surgical repair methods. Four animals were used to evaluate hemodynamic, behavioral, and neurological effects up to 5 days after SVC tear and repair. An occlusion balloon (Bridge Occlusion Balloon, Spectranetics Corporation, Colorado Springs, CO) was percutaneously delivered through the femoral vein to the location of the injury and inflated. Once hemodynamic control was achieved, the perforation was surgically repaired. RESULTS: After SVC perforation and clamp release, the rate of blood loss was 7.0 ± 0.8 mL/s. Mean time from SVC tear to occlusion balloon deployment was 55 ± 12 seconds, during which mean arterial pressure decreased from 56 ± 2 to 25 ± 3 mm Hg and heart rate decreased from 76 ± 7 to 62 ± 7 beats/min. After the deployment of the occlusion balloon, the rate of blood loss decreased by 90%, to 0.7 ± 0.2 mL/s. The mean time of balloon occlusion of the SVC was 16 ± 4 minutes and hemodynamic measures returned to baseline levels during this time. Study animals experienced no major complications, demonstrated stable recovery, and exhibited normal neurological function at each postoperative assessment. CONCLUSION: Endovascular temporary balloon occlusion may be a feasible option to reduce blood loss, maintain hemodynamic control, and provide a bridge to surgery after SVC injury.

Cellularity and structure of fresh human coronary thrombectomy specimens; presence of cells with markers of progenitor cells.

Acute coronary syndromes and acute myocardial infarctions are often related to plaque rupture and the formation of thrombi at the site of the rupture. We examined fresh coronary thrombectomy specimens from patients with acute coronary syndromes and assessed their structure and cellularity. The thrombectomy specimens consisted of platelets, erythrocytes and inflammatory cells. Several specimens contained multiple cholesterol crystals. Culture of thrombectomy specimens yielded cells growing in various patterns depending on the culture medium used. Culture in serum-free stem cell enrichment medium yielded cells with features of endothelial progenitor cells which survived in culture for a year. Immunohistochemical analysis of the thrombi revealed cells positive for CD34, cells positive for CD15 and cells positive for desmin in situ, whereas cultured cell from thrombi was desmin positive but pancytokeratin negative. Cells cultured in endothelial cell medium were von Willebrand factor positive. The content of coronary thrombectomy specimens is heterogeneous and consists of blood cells but also possibly cells from the vascular wall and cholesterol crystals. The culture of cells contained in the specimens yielded multiplying cells, some of which demonstrated features of haematopoietic progenitor cells and which differentiated into various cell-types.

Atrial fibrillation and mitral valve repair.

Atrial fibrillation (AF) is present in 30-40% of patients presenting for mitral valve surgery. In patients undergoing mitral valve repair, the presence of AF may be associated with increased mortality and morbidity and this is also the case in patients in whom AF persists postoperatively. Advances in understanding the pathogenesis of AF led to techniques that include both mitral valve repair and ablation of AF. The concomitant surgical treatment of AF during mitral surgery has become a commonly performed procedure, which was shown to be safe and which may improve the outcome for patients. AF after mitral valve replacement is an accepted indication for anticoagulation, but the data supporting anticoagulation in patients after mitral valverepair who convert to sinus rhythm are sparse. This article reviews the available data regarding outcomes of mitral repair and how they are influenced by AF and its therapy.

Gender differences in ventricular arrhythmia recurrence in patients with coronary artery disease and implantable cardioverter-defibrillators.

OBJECTIVES: We sought to determine whether men and women with coronary artery disease (CAD) and implantable cardioverter-defibrillators (ICDs) differ in frequency of arrhythmia recurrence and whether gender differences are independent of clinical, electrocardiographic, and electrophysiologic characteristics. BACKGROUND: Epidemiologic studies show that women have a lower rate of sudden cardiac death (SCD) than men, even among patients with CAD. Whether this is due to differing susceptibilities to ischemia or to arrhythmia is unknown. METHODS: The clinical records and ICD data disks of 340 men and 59 women with CAD who received an ICD between June 1990 and June 2000 were reviewed. Ventricular tachycardia (VT) or ventricular fibrillation (VF) recurrences were compared between genders and relationship with other factors was analyzed. RESULTS: Sustained VT/VF occurred in 52% of men and 34% of women (p < 0.01). Men experienced more total VT/VF events (p < 0.01), more shock-treated VT/VF events (p < 0.03), more electrical storms (p < 0.001), and had VT/VF on more days in follow-up (p < 0.01). Gender differences were independent of measured clinical, electrocardiographic, and electrophysiologic factors. In stratified analyses, the gender differences in VT/VF recurrence were greatest in patients presenting with sustained monomorphic VT and those with inducible VT at electrophysiology study. CONCLUSIONS: Women were less likely to experience VT/VF, and had fewer VT/VF episodes, than men. These findings were strongest in patients with evidence of a stable anatomic VT circuit: those with clinical or electrophysiologically induced VT. This study suggests that differing susceptibility to arrhythmia triggering may underlie the known differences in SCD rates between men and women.

Hyperkalemia induced T wave oversensing leading to loss of biventricular pacing and inappropriate ICD shocks.

Inappropriate ICD shocks remain a common problem. Double counting of single ventricular events can occur with biventricular ICDs implanted before univentricular sensing was available. Often this is due to a tachyarrhythmia or loss of left ventricular capture. This report describes a patient who developed hyperkalemia during hemodialysis, received inappropriate ICD shocks and experienced loss of biventricular pacing due to T wave rather than QRS double counting. Oversensing was abolished by reducing the potassium content of the dialysis bath. This underscores the need for careful interpretation of saved electrograms to determine the cause for, and appropriate treatment of, device related problems.