Inverse relation of body-surface activation-recovery interval and recovery time to activation time in normal subjects: stronger correlation and more heterogeneous distribution in activation-recovery interval than in recovery time

Electrophysiologic substrate and intraventricular left ventricular dyssynchrony in nonischemic heart failure patients undergoing cardiac resynchronization therapy

BACKGROUND

Electrocardiographic imaging (ECGI) is a method for noninvasive epicardial electrophysiologic mapping. ECGI previously has been used to characterize the electrophysiologic substrate and electrical synchrony in a very heterogeneous group of patients with varying degrees of coronary disease and ischemic cardiomyopathy.

OBJECTIVE

The purpose of this study was to characterize the left ventricular electrophysiologic substrate and electrical dyssynchrony using ECGI in a homogeneous group of nonischemic cardiomyopathy patients who were previously implanted with a cardiac resynchronization therapy (CRT) device.

METHODS

ECGI was performed during different rhythms in 25 patients by programming their devices to biventricular pacing, single-chamber (left ventricular or right ventricular) pacing, and native rhythm. The electrical dyssynchrony index (ED) was computed as the standard deviation of activation times at 500 sites on the LV epicardium.

RESULTS

In all patients, native rhythm activation was characterized by lines of conduction block in a region with steep activation-recovery interval (ARI) gradients between the epicardial aspect of the septum and LV lateral wall. A native QRS duration (QRSd) >130 ms was associated with high ED (≥30 ms), whereas QRSd <130 ms was associated with minimal (25 ms) to large (40 ms) ED. CRT responders had very high dyssynchrony (ED = 35.5 ± 3.9 ms) in native rhythm, which was significantly lowered (ED = 23.2 ± 4.4 ms) during CRT. All four nonresponders in the study did not show significant difference in ED between native and CRT rhythms.

CONCLUSION

The electrophysiologic substrate in nonischemic cardiomyopathy is consistent among all patients, with steep ARI gradients co-localizing with conduction block lines between the epicardial aspect of the septum and the LV lateral wall. QRSd wider than 130 ms is indicative of substantial LV electrical dyssynchrony; however, among patients with QRSd <130 ms, LV dyssynchrony may vary widely.

Diagnosis and ablation of atrial flutter using a high resolution, noncontact mapping system

The ablation of atrial flutter can sometimes be time consuming and unsuccessful using conventional catheter techniques especially in patients with recurrences after previous ablation procedures. Simultaneous high resolution mapping from multiple sites may overcome some of the limitations. Therefore, a new high resolution noncontact mapping system was used for diagnosis and ablation of atrial flutter in 15 patients. The mapping system consists of a catheter-mounted multielectrode array, an amplifier, and a computer workstation. Far-field potentials recorded by the multielectrode catheter are amplified, digitized, and sampled at 1.2 kHz, and digitally filtered to construct high resolution activation maps during tachycardia. Ablation catheters can be steered to target sites without fluoroscopy. In 12 of the 15 patients the analysis of the activation sequence during tachycardia showed a counter-clockwise, and in 1 of 15 patients a clockwise, rotating wavefront using the isthmus as part of the reentrant circuit. In two patients no tachycardia could be induced. In 3 of the 15 patients with previous conventional ablation procedures the gap in the line of block in the isthmus region was identified and marked on the animation model. The isthmus in the right atrium was ablated and isthmus block verified by the mapping system in all patients. No complications were observed. No recurrences of atrial flutter occurred during follow-up of 4 +/- 1.7 months. The total procedure and fluoroscopy time was 171 +/- 50.0 minutes and 24 +/- 12.7 minutes, respectively. In conclusion, the use of the new high resolution noncontact mapping system in patients with right atrial flutter is safe and highly effective. In patients with previously failed conventional ablation procedures the use of a noncontact mapping system may facilitate the identification of the gap in the line of block in the isthmus region and reablation of atrial flutter.