Rukshen Weerasooriya

Trends in incidence and prevalence of hospitalization for atrial fibrillation and associated mortality in Western Australia, 1995-2010

OBJECTIVE Hospitalization for atrial fibrillation (AF) is a large and growing public health problem. We examined current trends in the incidence, prevalence, and associated mortality of first-ever hospitalization for AF. METHODS Linked hospital admission data were used to identify all Western Australia residents aged 35-84 years with prevalent AF and incident (first-ever) hospitalization for AF as a principal or secondary diagnosis during 1995-2010. RESULTS There were 57,552 incident hospitalizations, mean age 69.8 years, with 41.4% women. Over the calendar periods, age- and sex-standardized incidence of hospitalization for AF as any diagnosis declined annually by 1.1% (95% CI; 0.93, 1.29), while incident AF as a principal diagnosis increased annually by 1.2% (95% CI; 0.84, 1.50). Incident AF hospitalization was higher among men than women, and 15-fold higher in the 75-84 compared with 35-64 year age group. The age- and sex-standardized prevalence of AF increased annually by 2.0% (95% CI; 1.88, 2.03) over the same period. Comorbidity trends were mixed with diabetes and valvular heart disease increasing, and hypertension, coronary artery disease, heart failure, cerebrovascular disease, and chronic kidney disease decreasing. The 1-year all-cause mortality after incident AF hospitalization declined from 17.6% to 14.6% (trend P<0.001), with an adjusted hazard ratio of 0.86 (95% CI; 0.81, 0.91). CONCLUSION This contemporary study shows that incident AF hospitalization is not increasing except for AF as a principal diagnosis, while population prevalence of hospitalized AF has risen substantially. The high 1-year mortality following incident AF hospitalization has improved only modestly over the recent period.

Irrigated Needle Ablation Creates Larger and More Transmural Ventricular Lesions Compared With Standard Unipolar Ablation in an Ovine Model

Background—Ventricular tachycardia recurrence can occur after ventricular tachycardia ablation because of incomplete and nontransmural ventricular lesion formation. We sought to compare the lesions made by a novel irrigated needle catheter to conventional radiofrequency lesions. Methods and Results—Thirteen female sheep (4.6±0.7 years, 54±8 kg) were studied. In 7 sheep, 60-s radiofrequency applications were performed using an irrigated needle catheter. In 6 sheep, conventional lesions were made using a 4-mm irrigated catheter. 1.5T in vivo and high-density magnetic resonance imaging (9.4T) were performed on explanted hearts from animals receiving needle radiofrequency. Conventional lesion volume was calculated as (1/6)×&pgr;×(A×B2+C×D2/2). Needle lesion volume was measured as &Sgr;(&pgr;×r2)/2 with a slice thickness of 1 mm. The dimensions of all lesions were also measured on gross pathology. Additional histological analysis of the needle lesions was performed. One hundred twenty endocardial left ventricular ablation lesions (conventional, n=60; needle, n=60) were created. At necropsy, more lesions were found using needle versus conventional radiofrequency (90% versus 75%; P<0.05). Comparing needle versus conventional radiofrequency: lesion volume was larger (1030±362 versus 488±384 mm3; P<0.001), lesion depth was increased (9.9±2.7 versus 5±2.4 mm; P<0.001), and more transmural lesions were created (62.5% versus 17%; P<0.01). Pericardial contrast injection was observed in 4 apical attempts using needle radiofrequency, however, with no adverse effects. Steam pops occurred in 3 attempts using conventional radiofrequency. Conclusions—Irrigated needle ablation is associated with more frequent, larger, deeper, and more often transmural lesions compared with conventional irrigated ablation. This technology might be of value to treat intramural or epicardial ventricular tachycardia substrates resistant to conventional ablation.

A new cryoenergy for ventricular tachycardia ablation: a proof-of-concept study.

Introduction Lack of transmural lesion formation during radiofrequency (RF) ablation for ventricular tachycardia (VT) is an important determinant of arrhythmia recurrence. The aim of this proof-of-concept study was to evaluate safety and efficacy of a new and more powerful cryoablation system for ventricular ablation. Methods and results Five healthy female sheep (59 ± 6 kg) underwent a surgical sternotomy for epicardial and endocardial access [endocardial access via right atrial appendage and left ventricular (LV) apex]. A cryoablation system with liquid nitrogen (IceCure) was used to create 3 min freezes at the right ventricle (RV). Left ventricular cryoablation was performed with either a 6 min or 2 × 4 min freezes. To assess safety, ablation was also performed on the mid left anterior descending artery and the proximal coronary sinus. A total of 45 lesions were created (RV epicardial, n = 12; LV epicardial, n = 18; RV endocardial, n = 7; LV endocardial, n = 8; LAD, n = 4; and CS, n = 4). The mean lesion volume was 5055 ± 92 mm3 (length: 32 ± 4.6 mm, width: 16.0 ± 6.4 mm, and depth: 11.2 ± 4.4 mm). Lesions were transmural in 28/45 (62%) and >10 mm in depth in 35/45 (78%). Of the endocardial lesions, 12/15 were transmural (80%). There was no benefit of the bonus freeze in LV lesions (6 vs. 2 × 4 min: 6790 ± 44 vs. 5595 ± 63 mm3; P = 0.44). All ablated vascular structures appeared macroscopically normal without acute stenosis. One animal died due to incessant Ventricular fibrillation (VF). Conclusion Our results indicate that a more powerful cryoablation system is able to create large, transmural ventricular lesions from both the endocardium and the epicardium. The technology may hold potential for both surgical and catheter-based VT ablation in humans.