Humera Ahmed

Renal Sympathetic Denervation Using an Irrigated Radiofrequency Ablation Catheter for the Management of Drug-Resistant Hypertension

OBJECTIVES This study sought to assess whether renal sympathetic denervation (RSDN) can be achieved using an off-the-shelf saline-irrigated radiofrequency ablation (RFA) catheter typically employed for cardiac tissue ablation. BACKGROUND RSDN using a specialized solid-tip RFA catheter has recently been demonstrated to safely reduce systemic blood pressure in patients with refractory hypertension. For cardiac tissue ablation, RFA technology has evolved from nonirrigated to saline-irrigated ablation electrodes to improve both safety and effectiveness. METHODS Ten patients with resistant hypertension underwent renal angiography, followed by bilateral RSDN with a saline-irrigated RFA catheter. Ambulatory blood pressure recordings (24 h) were obtained at baseline, 1, 3, and 6 months after the procedure. Repeat renal angiography was performed during follow-up to assess for arterial stenosis or aneurysm. In 5 patients, pre- and post-procedural serum measures of renal function and sympathetic activity were obtained: aldosterone; metanephrine; normetanephrine; plasma renin activity; and creatinine. RESULTS Over a 6-month period: 1) the systolic/diastolic blood pressure decreased by -21/-11 mm Hg; 2) all patients experienced a decrease in systolic blood pressure of at least 10 mm Hg (range 10 to 40 mm Hg); 3) there was no evidence of renal artery stenosis or aneurysm at repeat angiography; and 4) there was a significant decrease in metanephrine (-12 ± 4, p = 0.003), normetanephrine (-18 ± 4, p = 0.0008), and aldosterone levels (-60 ± 33 ng/l, p = 0.02) at 3 months. There was no significant change in plasma renin activity (-0.2 mg/l/hod, p = 0.4). There was no significant change in serum creatinine (-1 mmol/l, p = 0.4). CONCLUSIONS These data provide the proof-of-principle that RSDN can be performed using an off-the-shelf saline-irrigated RFA catheter.

The esophageal effects of cryoenergy during cryoablation for atrial fibrillation.

BACKGROUND Cryoenergy is being increasingly used for atrial fibrillation (AF) ablation, but the thermal effect of cryoenergy on the esophagus remains undefined. OBJECTIVE This study examines the esophageal effects of cryoenergy used during AF ablation. METHODS Catheter ablation was performed using a cryoballoon catheter in 67 AF patients (Cryoballoon group), and a spot cryocatheter to complete irrigated radiofrequency lesion sets at segments in close proximity to the esophagus in 7 AF patients (Cryo-Focal group). A temperature probe monitored the luminal esophageal temperature (LET) in all patients; LET changes did not guide therapy. Post-procedural endoscopy was performed on 35 of 67 (52%) Cryoballoon and all Cryo-Focal patients. RESULTS Significant LET decreases (>1 degrees C) occurred in 62 of 67 (93%) Cryoballoon patients. LET continued to decrease after termination of cryoablation before recovering to normal. Temperature decreases were more pronounced during ablation at the inferior (3.1 degrees C) than superior pulmonary veins (1.5 degrees C); the lowest observed temperature was 0 degrees C. Post-procedural endoscopy showed esophageal ulcerations in 6 of 35 (17%) patients. There were no atrial-esophageal fistulas, and all ulcers had healed on follow-up endoscopy. Patients with and without ulceration differed with respect to mean LET nadir, cumulative LET decrease, and number of LETs <30 degrees C. In the Cryo-Focal group, 6 +/- 2 spot cryolesions per patient resulted in 1.3 +/- 1 LET decreases per patient, and an absolute nadir of 32.5 degrees C. CONCLUSION Cryoballoon ablation can cause significant LET decreases, resulting in reversible esophageal ulcerations in 17% of patients. No ulcerations occurred with adjunctive spot cryoablation at regions near the esophagus during radiofrequency ablation procedures.

Catheter ablation of atrial fibrillation without the use of fluoroscopy

BACKGROUND In performing catheter ablation of paroxysmal atrial fibrillation (PAF), the advent of electroanatomical mapping (EAM) has significantly reduced fluoroscopy time. Recent advances in the ability of EAM systems to simultaneously visualize multiple catheters have allowed some operators to perform certain procedures, such as catheter ablation of supraventricular tachycardias, with zero fluoroscopy use. OBJECTIVE The purpose of this study was to evaluate the feasibility and safety of pulmonary vein (PV) isolation with zero fluoroscopy use, using a combination of three-dimensional EAM and intracardiac echocardiography (ICE). METHODS Using the NavX EAM system, the right atrial (RA) and coronary sinus (CS) geometries were created without fluoroscopy. Fluoroless transseptal puncture was performed under ICE guidance. Using a deflectable sheath and a multipolar catheter, the left atrial (LA) and PV anatomies were rendered and, in select cases, integrated with a three-dimensional computed tomography (CT) image. Irrigated radiofrequency ablation was performed to encircle each pair of ipsilateral PVs. RESULTS This series included 20 consecutive PAF patients. RA/CS mapping required 5.5 ± 2.6 minutes. In all patients, single (n = 18) or dual (n = 2) transseptal access was successfully achieved. The LA-PV anatomy was rendered using either a circular (14 patients) or penta-array (six patients) catheter in 22 ± 10 minutes; CT image integration was used in 11 patients. Using 49 ± 18 ablation lesions/patient, electrical isolation was achieved in 38/39 ipsilateral PV isolating lesion sets (97%). The procedure time was 244 ± 75 minutes. There were no complications. CONCLUSION Completely fluoroless catheter ablation of paroxysmal AF is safely feasible using a combination of ICE and EAM.

Adjunctive Renal Sympathetic Denervation to Modify Hypertension as Upstream Therapy in the Treatment of Atrial Fibrillation (H-FIB) Study: Clinical Background and Study Design

Hypertension is the most important risk factor directly attributable to the high prevalence of atrial fibrillation (AF), and is one of the few modifiable risk factors for AF. Activation and overactivity of the sympathetic nervous system (SNS) have been implicated in the pathogenesis of both essential hypertension and AF. Catheter‐based renal sympathetic denervation (RSDN) appears to be an effective adjunctive treatment for refractory hypertension, and may be beneficial in other conditions characterized by SNS overactivity, such as left ventricular hypertrophy and atrial arrhythmias.

Initial clinical experience with a novel visualization and virtual electrode radiofrequency ablation catheter to treat atrial flutter

BACKGROUND Linear ablation lesions are used to treat a variety of cardiac arrhythmias. However, successful long-term outcome is hampered by both the uncertainty of catheter-tissue contact for any individual lesion and the difficulty in ensuring point-to-point lesion contiguity. OBJECTIVE A novel virtual electrode radiofrequency ablation catheter equipped with an endoscope to directly visualize the target tissue was used to ensure tissue contact and lesion contiguity along the cavotricuspid isthmus (CTI) to treat typical atrial flutter. METHODS In this feasibility study of five patients with drug-resistant CTI-dependent atrial flutter, catheter ablation was performed using the visualization virtual electrode radiofrequency ablation catheter. After standard femoral access, the ablation catheter was advanced to the tricuspid annulus under fluoroscopic and intracardiac echocardiography guidance. In three of five patients, the ablation procedure was performed during atrial flutter; the other two ablations were during coronary sinus pacing. RESULTS Conversion to sinus rhythm was noted after the delivery of 12 ± 7 lesions. Bidirectional CTI conduction block was successfully achieved in all patients. Initial, transient CTI block was first observed after delivering 19 ± 13 lesions; ultimately, 34 ± 18 lesions were required to achieve permanent bidirectional CTI block. The mean ablation and procedure times were 72 ± 42 and 151 ± 17 minutes. The mean fluoroscopy times for the ablation alone and the entire procedure were 13 ± 8 and 17 ± 7 minutes, respectively. CONCLUSIONS This study introduces the clinical feasibility of a novel paradigm for contiguous linear ablation: virtual electrode ablation under direct endoscopic visualization.

Ambulatory Monitoring and Arrhythmic Outcomes in Pediatric and Adolescent Patients With Duchenne Muscular Dystrophy

Background Patients with Duchenne Muscular Dystrophy (DMD) develop cardiac fibrosis and dilated cardiomyopathy. We described the frequency of significant Holter findings in DMD, the relationship between cardiac function and arrhythmia burden, and the impact of these findings on clinical management. Methods and Results A retrospective review was done of patients with DMD who received a Holter from 2010 to 2014. Clinical and arrhythmic outcomes were analyzed. Patients were classified based on left ventricular ejection fraction (LVEF): ≥55%, 35% to 54% and <35%. Significant Holter findings included atrial tachycardia, ventricular tachycardia and atrial fibrillation/flutter. Logistic regression was used to assess predictors of significant Holter findings and change in care. The study included 442 Holters in 235 patients. Mean age was 14±4 years. Patients with cardiac dysfunction were older, and had increased late gadolinium enhancement and left ventricular dilation (P<0.01). There were 3 deaths (1%), all with normal function and none cardiac. Patients with LVEF <35% had more arrhythmias including nonsustained atrial tachycardia (P=0.01), frequent premature ventricular contractions, ventricular couplets/triplets, and nonsustained ventricular tachycardia (P<0.001) compared to the other groups. LVEF <35% (P<0.001) was the only predictor of clinically significant Holter finding. Four patients (40%) had change in medication in the LVEF <35% group compared to 9 (3%) in the ≥55% and 4 (4%) in the 35% to 54% groups (P<0.001). Conclusions Sudden cardiac events are rare in DMD patients with an LVEF >35%. Significant Holter findings are rare in patients with DMD who have an LVEF >35%, and cardiac dysfunction appears to predict significant Holter findings. Holter monitoring is highest yield among DMD patients with cardiac dysfunction.