An entirely subcutaneous implantable cardioverter-defibrillator.

BACKGROUND: Implantable cardioverter-defibrillators (ICDs) prevent sudden death from cardiac causes in selected patients but require the use of transvenous lead systems. To eliminate the need for venous access, we designed and tested an entirely subcutaneous ICD system. METHODS: First, we conducted two short-term clinical trials to identify a suitable device configuration and assess energy requirements. We evaluated four subcutaneous ICD configurations in 78 patients who were candidates for ICD implantation and subsequently tested the best configuration in 49 additional patients to determine the subcutaneous defibrillation threshold in comparison with that of the standard transvenous ICD. Then we evaluated the long-term use of subcutaneous ICDs in a pilot study, involving 6 patients, which was followed by a trial involving 55 patients. RESULTS: The best device configuration consisted of a parasternal electrode and a left lateral thoracic pulse generator. This configuration was as effective as a transvenous ICD for terminating induced ventricular fibrillation, albeit with a significantly higher mean (+/-SD) energy requirement (36.6+/-19.8 J vs. 11.1+/-8.5 J). Among patients who received a permanent subcutaneous ICD, ventricular fibrillation was successfully detected in 100% of 137 induced episodes. Induced ventricular fibrillation was converted twice in 58 of 59 patients (98%) with the delivery of 65-J shocks in two consecutive tests. Clinically significant adverse events included two pocket infections and four lead revisions. After a mean of 10+/-1 months, the device had successfully detected and treated all 12 episodes of spontaneous, sustained ventricular tachyarrhythmia. CONCLUSIONS: In small, nonrandomized studies, an entirely subcutaneous ICD consistently detected and converted ventricular fibrillation induced during electrophysiological testing. The device also successfully detected and treated all 12 episodes of spontaneous, sustained ventricular tachyarrhythmia. (ClinicalTrials.gov numbers, NCT00399217 and NCT00853645.)

Giant congenital coronary artery aneurysm in pulmonary atresia with intact septum.

Congenital coronary artery fistula is frequently associated with pulmonary atresia and intact ventricular septum (PA/IVS). Aneurysmal dilatation is rare, and can be complicated by rupture, distal thrombi and myocardial ischaemia.

Relationship between voltage map "channels" and the location of critical isthmus sites in patients with post-infarction cardiomyopathy and ventricular tachycardia.

OBJECTIVES: The goal of this study was to determine the relationship of the ventricular tachycardia (VT) isthmus to channels of preserved voltage on an electroanatomic voltage map in postinfarction cardiomyopathy. BACKGROUND: Substrate mapping in patients with postinfarction cardiomyopathy and VT may involve lowering the voltage cutoff that defines the scar (<1.5 mV) to identify "channels" of relative higher voltage within the scar. However, the prevalence of channels within the scar identified by using electroanatomic mapping and the relationship to the protected VT isthmus identified by entrainment mapping is unknown. METHODS: Detailed bipolar endocardial voltage maps (398 ± 152 points) from 24 patients (mean age 69 ± 9 years) with postinfarction cardiomyopathy (ejection fraction 33 ± 9%) and tolerated VT were reviewed. Endocardial scar was defined according to voltage <1.5 mV. Isolated late potentials (ILPs) were identified and tagged on the electroanatomic voltage map. The baseline voltage cutoffs were then adjusted until all channels were identified. The VT isthmus was identified using entrainment mapping. RESULTS: Inferior and anterior/lateral infarction was present by voltage mapping in 18 and 6 patients, respectively (scar area 44 ± 24 cm(2)). By adjusting voltage cutoffs, 37 channels were identified in 21 (88%) of 24 patients. The presence of ILPs within a channel was seen in 11 (46%) of 24 patients and 17 (46%) of 37 channels. A VT isthmus site was contained within a channel in only 11 of 24 patients or 11 of 37 channels. No difference in voltage characteristics was identified between clinical and nonclinical channels. Voltage channels with ILPs harbored the clinical isthmus with a sensitivity and specificity of 78% and 85%, respectively. CONCLUSIONS: Channels were identified in 88% of patients with VT by adjusting the voltage limits of bipolar maps; however, the specificity of those channels in predicting the location of VT isthmus sites was only 30%. The presence of ILPs inside the voltage channel significantly increases the specificity for identifying the clinical VT isthmus.

Influence of left ventricular hypertrophy on scar identification during bipolar voltage mapping.

PURPOSE: Bipolar endocardial signal amplitude (BESA) <1.5 mV defines scar in the left ventricle (LV). It is not known if LV hypertrophy (LVH) increases overall bipolar signal amplitude and if scar identification with LVH requires a higher voltage cutoff. METHODS: We compared the LV BESA of four patients with moderate LVH on echo (≥1.6 cm) to that of ten consecutive patients with no LVH with both groups having normal systolic function and no scar. Additionally, in 12 patients with ischemic scar (ICM) and moderate LVH (≥1.6 cm), we assessed scar area and percent abnormal electrograms (width >80 ms and/or split/fractionated) using 1.5 and 2.5 mV defined border zone cutoff values and compared results to those from 12 ICM patients with no LVH matched for age, sex, scar distribution, and LV ejection fraction. RESULTS: Average BESA in the setting of normal systolic function/no scar was comparable in patients with (4.7 ± 3.0 mV, 95% signals >1.58 mV) and those without LVH (4.9 ± 1.6 mV, 95% signals >1.62 mV). In patients with ICM and LVH versus without LVH, there was a smaller area of dense scar <0.5 mV/total scar (15% versus 23%, p = 0.03) but no significant difference in the size of the border zone, or percentage of abnormal electrograms identified within border zones defined by either the 0.5-1.5 mV or 0.5-2.5 mV cutoff values. CONCLUSIONS: Patients with and without LVH with normal systolic function show similar LV endocardial bipolar signal characteristics. Modifying the bipolar amplitude cutoff at the infarct border zone did not increase overall scar size in patients with versus those without LVH. A 1.5 mV-bipolar voltage cutoff used for scar definition seems appropriate even in patients with marked LVH.

Ablation of ventricular arrhythmias arising near the anterior epicardial veins from the left sinus of Valsalva region: ECG features, anatomic distance, and outcome.

BACKGROUND: Left ventricular outflow tract tachycardia/premature depolarizations (VT/VPDs) arising near the anterior epicardial veins may be difficult to eliminate through the coronary venous system. OBJECTIVE: To describe the characteristics of an alternative successful ablation strategy targeting the left sinus of Valsalva (LSV) and/or the adjacent left ventricular (LV) endocardium. METHODS: Of 276 patients undergoing mapping/ablation for outflow tract VT/VPDs, 16 consecutive patients (8 men; mean age 52 ± 17 years) had an ablation attempt from the LSV and/or the adjacent LV endocardium for VT/VPDs mapped marginally closer to the distal great cardiac vein (GCV) or anterior interventricular vein (AIV). RESULTS: Successful ablation was achieved in 9 of the 16 patients (56%) targeting the LSV (5 patients), adjacent LV endocardium (2 patients), or both (2 patients). The R-wave amplitude ratio in lead III/II and the Q-wave amplitude ratio in aVL/aVR were smaller in the successful group (1.05 ± 0.13 vs 1.34 ± 0.37 and 1.24 ± 0.42 vs 2.15 ± 1.05, respectively; P = .043 for both). The anatomical distance from the earliest GCV/AIV site to the closest point in the LSV region was shorter for the successful group (11.0 ± 6.5 mm vs 20.4 ± 12.1 mm; P = .048). A Q-wave ratio of <1.45 in aVL/aVR and an anatomical distance of <13.5 mm had sensitivity and specificity of 89%, 75% and 78%, 64%, respectively, for the identification of successful ablation. CONCLUSIONS: VT/VPDs originating near the GCV/AIV can be ablated from the LSV/adjacent LV endocardium. A Q-wave ratio of <1.45 in aVL/aVR and a close anatomical distance of <13.5 mm help identify appropriate candidates.

The V(2) transition ratio: a new electrocardiographic criterion for distinguishing left from right ventricular outflow tract tachycardia origin.

OBJECTIVES: We sought to develop electrocardiography (ECG) criteria for distinguishing left ventricular outflow tract (LVOT) from right ventricular outflow tract (RVOT) origin in patients with idiopathic outflow tract ventricular tachycardia (OTVT) and lead V(3) R/S transition. BACKGROUND: Several ECG criteria have been proposed for differentiating left from right OTVT origin; ventricular tachycardias (VTs) with left bundle branch block and V(3) transition remain a challenge. METHODS: We analyzed the surface ECG pattern of patients with OTVT with a precordial transition in lead V(3) who underwent successful catheter ablation. Sinus and VT QRS morphologies were measured in limb and precordial leads with electronic calipers. The V(2) and V(3) transition ratios were calculated by computing the percentage R-wave during VT (R/R+S)(VT) divided by the percentage R-wave in sinus rhythm (R/R+S)(SR). RESULTS: We retrospectively analyzed ECGs from 40 patients (mean age 44 ± 14 years, 21 female) with outflow tract premature ventricular contractions (PVCs)/VT. Patients with structural heart disease, paced rhythms, and bundle branch block during sinus rhythm were excluded. The V(2) transition ratio was significantly greater for LVOT PVCs compared with RVOT PVCs (1.27 ± 0.60 vs. 0.23 ± 0.16; p < 0.001) and was the only independent predictor of LVOT origin. In 21 prospective cases, a V(2) transition ratio ≥0.60 predicted an LVOT origin with 91% accuracy. A PVC precordial transition occurring later than the sinus rhythm transition excluded an LVOT origin with 100% accuracy. CONCLUSIONS: The V(2) transition ratio is a novel electrocardiographic measure that reliably distinguishes LVOT from RVOT origin in patients with lead V(3) precordial transition. This measure might be useful for counseling patients and planning an ablation strategy.