Larry Chinitz

Early performance of a miniaturized leadless cardiac pacemaker: the Micra Transcatheter Pacing Study

Aims Permanent cardiac pacing is the only effective treatment for symptomatic bradycardia, but complications associated with conventional transvenous pacing systems are commonly related to the pacing lead and pocket. We describe the early performance of a novel self-contained miniaturized pacemaker. Methods and results Patients having Class I or II indication for VVI pacing underwent implantation of a Micra transcatheter pacing system, from the femoral vein and fixated in the right ventricle using four protractible nitinol tines. Prespecified objectives were >85% freedom from unanticipated serious adverse device events (safety) and <2 V 3-month mean pacing capture threshold at 0.24 ms pulse width (efficacy). Patients were implanted (n = 140) from 23 centres in 11 countries (61% male, age 77.0 ± 10.2 years) for atrioventricular block (66%) or sinus node dysfunction (29%) indications. During mean follow-up of 1.9 ± 1.8 months, the safety endpoint was met with no unanticipated serious adverse device events. Thirty adverse events related to the system or procedure occurred, mostly due to transient dysrhythmias or femoral access complications. One pericardial effusion without tamponade occurred after 18 device deployments. In 60 patients followed to 3 months, mean pacing threshold was 0.51 ± 0.22 V, and no threshold was ≥2 V, meeting the efficacy endpoint (P < 0.001). Average R-wave was 16.1 ± 5.2 mV and impedance was 650.7 ± 130 ohms. Conclusion Early assessment shows the transcatheter pacemaker can safely and effectively be applied. Long-term safety and benefit of the pacemaker will further be evaluated in the trial. Clinical Trial Registration ClinicalTrials.gov ID NCT02004873.

Comparison of cardiac catheterization and Doppler echocardiography in the decision to operate in aortic and mitral valve disease

Clinical decisions utilizing either Doppler echocardiographic or cardiac catheterization data were compared in adult patients with isolated or combined aortic and mitral valve disease. A clinical decision to operate, not operate or remain uncertain was made by experienced cardiologists given either Doppler echocardiographic or cardiac catheterization data. A prospective evaluation was performed on 189 consecutive patients (mean age 67 years) with valvular heart disease who were being considered for surgical treatment on the basis of clinical information. All patients underwent cardiac catheterization and detailed Doppler echocardiographic examination. Three sets of two cardiologist decision makers who did not know patient identity were given clinical information in combination with either Doppler echocardiographic or cardiac catheterization data. The combination of Doppler echocardiographic and clinical data was considered inadequate for clinical decision making in 21% of patients with aortic and 5% of patients with mitral valve disease. The combination of cardiac catheterization and clinical data was considered inadequate in 2% of patients with aortic and 2% of patients with mitral valve disease. Among the remaining patients, the cardiologists using echocardiographic or angiographic data were in agreement on the decision to operate or not operate in 113 (76% overall). When the data were analyzed by specific valve lesion, decisions based on Doppler echocardiography or catheterization were in agreement in 92%, 90%, 83% and 69%, respectively, of patients with aortic regurgitation, mitral stenosis, aortic stenosis and mitral regurgitation. Differences in cardiac output determination, estimation of valvular regurgitation and information concerning coronary anatomy were the main reasons for different clinical management decisions. These results suggest that for most adult patients with aortic or mitral valve disease, alone or in combination, Doppler echocardiographic data enable the clinician to make the same decision reached with catheterization data.

Percutaneous left ventricular assist devices in ventricular tachycardia ablation: multicenter experience.

Background—Data on relative safety, efficacy, and role of different percutaneous left ventricular assist devices for hemodynamic support during the ventricular tachycardia (VT) ablation procedure are limited. Methods and Results—We performed a multicenter, observational study from a prospective registry including all consecutive patients (N=66) undergoing VT ablation with a percutaneous left ventricular assist devices in 6 centers in the United States. Patients with intra-aortic balloon pump (IABP group; N=22) were compared with patients with either an Impella or a TandemHeart device (non-IABP group; N=44). There were no significant differences in the baseline characteristics between both the groups. In non-IABP group (1) more patients could undergo entrainment/activation mapping (82% versus 59%; P=0.046), (2) more number of unstable VTs could be mapped and ablated per patient (1.05±0.78 versus 0.32±0.48; P<0.001), (3) more number of VTs could be terminated by ablation (1.59±1.0 versus 0.91±0.81; P=0.007), and (4) fewer VTs were terminated with rescue shocks (1.9±2.2 versus 3.0±1.5; P=0.049) when compared with IABP group. Complications of the procedure trended to be more in the non-IABP group when compared with those in the IABP group (32% versus 14%; P=0.143). Intermediate term outcomes (mortality and VT recurrence) during 12±5-month follow-up were not different between both groups. Left ventricular ejection fraction ⩽15% was a strong and independent predictor of in-hospital mortality (53% versus 4%; P<0.001). Conclusions—Impella and TandemHeart use in VT ablation facilitates extensive activation mapping of several unstable VTs and requires fewer rescue shocks during the procedure when compared with using IABP.

Genetically engineered SCN5A mutant pig hearts exhibit conduction defects and arrhythmias

SCN5A encodes the α subunit of the major cardiac sodium channel Na(V)1.5. Mutations in SCN5A are associated with conduction disease and ventricular fibrillation (VF); however, the mechanisms that link loss of sodium channel function to arrhythmic instability remain unresolved. Here, we generated a large-animal model of a human cardiac sodium channelopathy in pigs, which have cardiac structure and function similar to humans, to better define the arrhythmic substrate. We introduced a nonsense mutation originally identified in a child with Brugada syndrome into the orthologous position (E558X) in the pig SCN5A gene. SCN5A(E558X/+) pigs exhibited conduction abnormalities in the absence of cardiac structural defects. Sudden cardiac death was not observed in young pigs; however, Langendorff-perfused SCN5A(E558X/+) hearts had an increased propensity for pacing-induced or spontaneous VF initiated by short-coupled ventricular premature beats. Optical mapping during VF showed that activity often began as an organized focal source or broad wavefront on the right ventricular (RV) free wall. Together, the results from this study demonstrate that the SCN5A(E558X/+) pig model accurately phenocopies many aspects of human cardiac sodium channelopathy, including conduction slowing and increased susceptibility to ventricular arrhythmias.

Standardization and validation of an automated algorithm to identify fractionation as a guide for atrial fibrillation ablation

BACKGROUND Atrial fibrillation catheter ablation is frequently guided by identification of fractionated electrograms, which are thought to be critical for maintenance of the arrhythmia. Objective automated means for identifying fractionation independent of physician interpretation have not been standardized or validated. OBJECTIVE The purpose of this study was to standardize and validate an automated algorithm to rapidly identify fractionated electrograms for high-density atrial fibrillation fractionation mapping. METHODS Left and right atrial fractionation maps were generated by EnSite NavX 6.0 software, using standardized ablation catheters in eight patients with atrial fibrillation. Two blinded electrophysiologists interpreted all electrograms as either fractionated or not fractionated. A stepwise approach was used to optimize automated settings to accurately identify fractionation. High-density fractionation maps were generated with a 20-pole mapping catheter in eight other patients. Two blinded electrophysiologists interpreted all electrograms as near field or far field. The algorithm was refined to optimize settings to exclude far-field signals and retain near-field signals. The sampling segment length was adjusted to optimize recording time to ensure reproducibility. RESULTS Using 1,514 points, the automated software achieved sensitivity of 0.75 and specificity of 0.80 for identification of fractionated electrograms. Using 725 points collected via multipole catheters with optimal automated settings, 94% of near-field fractionated electrograms were accurately identified. A 6-second sampling length was needed for reproducible fractionation measurements. CONCLUSION Standardized settings of EnSite NavX 6.0 software with 6-second data collection per point can rapidly and accurately generate high-density fractionation maps independent of physician electrogram interpretation. This may allow for an automated, standardized approach to atrial fibrillation fractionated ablation.

Contact Sensing Provides a Highly Accurate Means to Titrate Radiofrequency Ablation Lesion Depth

RF Ablation Lesion Depth Estimation Using Contact Sensing. Background: Transmural lesions are essential for efficacious ablation. There are, however, no accurate means to estimate lesion depth.

Spinal cord stimulation protects against atrial fibrillation induced by tachypacing

BACKGROUND Spinal cord stimulation (SCS) has been shown to modulate atrial electrophysiology and confer protection against ischemia and ventricular arrhythmias in animal models. OBJECTIVE To determine whether SCS reduces the susceptibility to atrial fibrillation (AF) induced by tachypacing (TP). METHODS In 21 canines, upper thoracic SCS systems and custom cardiac pacing systems were implanted. Right atrial and left atrial effective refractory periods were measured at baseline and after 15 minutes of SCS. Following recovery in a subset of canines, pacemakers were turned on to induce AF by alternately delivering TP and searching for AF. Canines were randomized to no SCS therapy (CTL) or intermittent SCS therapy on the initiation of TP (EARLY) or after 8 weeks of TP (LATE). AF burden (percent AF relative to total sense time) and AF inducibility (percentage of TP periods resulting in AF) were monitored weekly. After 15 weeks, echocardiography and histology were performed. RESULTS Effective refractory periods increased by 21 ± 14 ms (P = .001) in the left atrium and 29 ± 12 ms (P = .002) in the right atrium after acute SCS. AF burden was reduced for 11 weeks in EARLY compared with CTL (P <.05) animals. AF inducibility remained lower by week 15 in EARLY compared with CTL animals (32% ± 10% vs 91% ± 6%; P <.05). AF burden and inducibility were not significantly different between LATE and CTL animals. There were no structural differences among any groups. CONCLUSIONS SCS prolonged atrial effective refractory periods and reduced AF burden and inducibility in a canine AF model induced by TP. These data suggest that SCS may represent a treatment option for AF.

Endoventricular remodeling of left ventricular aneurysm. Functional, clinical, and electrophysiological results.

BACKGROUND Recent advances in surgical techniques for the repair of left ventricular aneurysms (LVAs) include the use of an endoventricular patch to exclude the aneurysm cavity. This technique has replaced conventional linear plication of the aneurysm. The endoventricular patch technique remodels the left ventricular cavity to a more physiological geometry that improves function. METHODS AND RESULTS From December 1989 through November 1993, 45 patients underwent an LVA repair with an endoventricular patch. This procedure was performed in association with coronary artery bypass grafting in 40 patients. Twenty-eight patients (62.2%) also had nonguided encircling subendocardial incisions. Operative procedures included 7 emergency operations, 3 concomitant valve procedures, and a mean of 2.2 bypass grafts per patient. Eight patients had previous cardiac operations. Hospital mortality was 15.6% (7/45) for all patients and 9.1% (3/33) for nonemergent revascularization and LVA repairs. Ejection fraction improved from a mean of 25.8% preoperatively to 37.8% postoperatively; the mean New York Heart Association classification improved from 3.5 to 1.5. Of patients known to have preoperative arrhythmias (inducible or sudden death), 69% were not inducible postoperatively without antiarrhythmic medication. Survival from late cardiac death (including death of unknown origin) was 86.5% at 2 years. Freedom from documented ventricular arrhythmias was 94.3% at 2 years. CONCLUSIONS These results indicate that the patch endoaneurysmorrhaphy technique can provide an excellent functional and physiological outcome in patients with LVAs and severely impaired ventricular function.

Echocardiographic evaluation of the coronary sinus.

The purpose of this study was to compare transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE) in the evaluation of the coronary sinus and its blood flow. Forty patients were studied by TTE and TEE. The distal coronary sinus and its right atrial communication could be identified in 21 of 40 by TTE, and in all patients by TEE. Coronary sinus diameter measurement at the right atrial communication was possible by TTE in 16 of 40, and in all patients by TEE (maximal diameter 6 to 14 mm, mean 9 +/- 2). Flow velocity measurement by pulsed Doppler was possible in 25 of 40 patients (63%) by TEE, and in none by TTE. The flow velocity pattern was similar to central vein flow velocity, with systolic and diastolic antegrade waves, and a small retrograde end diastolic wave. The coronary sinus cross-sectional area was measured in 5 patients by intravascular ultrasound. It varied in size and shape during the cardiac cycle, reaching a maximum (0.3 to 1.5 cm2) at end diastole, and decreasing by 40% to 70% at end systole. TEE is superior to TTE in the evaluation of the coronary sinus and its blood flow velocity. However, because of the variability in cross-sectional area size and shape, measurement of coronary sinus blood flow may be inaccurate.

Mapping Reentry Around Atriotomy Scars Using Double Potentials

Supraventricular arrhythmias, often seen in patients after cardiac surgery, may be associated with scars produced in the atria at the time of surgery. Double potentials, found in the presence of functional or anatomical block, can define the limits and critical regions of a reentrant circuit associated with the atriotomy scars. We describe six patients with seven distinct atrial tachycardias in whom atriotomy scars were successfully mapped during intraatrial reentry utilizing the presence and interelectrogram relationship of observed double potentials. The reentrant circuit was mapped in all patients by following the relationship between double potentials along the surgical scar, assuming that they would be widely split in the middle of the scar and merge into a single continuous fractionated potential at the apex of the scar. At this site, atrial pacing was performed to entrain the tachycardia and confirm the participation of the atriotomy scar in the clinically relevant atrial tachycardia. Radiofrequency ablation was performed from the site of electrogram fusion to the nearest anatomical obstacle. Five of seven atrial tachycardias were successfully ablated utilizing this technique over a mean follow‐up of 10 months. We proposed that these double potentials and their interelectrogram relationship are an effective means of mapping atriotomy scars and guiding successful radiofrequency ablation.