Factors Influencing Diaphragmatic Compound Motor Action Potentials During Cryoballoon Ablation for Atrial Fibrillation.

INTRODUCTION: The diaphragmatic compound motor action potentials (CMAPs) have been used to predict and prevent phrenic nerve injury (PNI) during cryoballoon ablation of right pulmonary veins. We sought to assess factors that influence the amplitude of the surface CMAP recordings. METHODS AND RESULTS: We analyzed CMAPs from consecutive patients undergoing cryoballoon ablation for paroxysmal atrial fibrillation. CMAP recordings were obtained using electrocardiography electrodes positioned in the "modified lead I" method while stimulating the right PN, until loss of capture (ascertained by palpation and fluoroscopy of the right hemi-diaphragm). A total of 55 patients (age 63 ± 11 years; 60% men; body mass index [BMI] 31 ± 6) had adequate CMAP recordings and were included for evaluation of CMAP signals. CMAPs demonstrated 2 distinct components, an early higher amplitude signal (pacing artifact) and a later lower amplitude signal (true diaphragmatic CMAP). There was no significant change in the true CMAP recording amplitude with decrease in stimulus strength (P = 0.1). There was no impact of BMI on CMAP amplitude (P = 0.93). There was a significant phasic respiratory variation in CMAP amplitude with a mean decrease in CMAP amplitude of 10.8% (range: 8-12%) with inspiration lasting an average of 2 beats (P < 0.001). A decrease in CMAP amplitude of >30% was noted in 6 cases (11%) and termination of cryoablation prevented PNI. CONCLUSION: Diaphragmatic CMAP amplitude is not affected by stimulus strength or BMI. There is a significant respirophasic decrease in CMAP signal amplitude with inspiration. It is important to be aware of this variation to avoid premature termination of cryoablation.

A Practical ECG Criterion to Unmask Left Accessory AV Connections in Patients With Subtle Preexcitation.

BACKGROUND: Accessory AV-connections capable of antegrade conduction need to be recognized because of the potential for life-threatening arrhythmias. However, the preexcited ECG pattern may be subtle, especially among left-sided AV-connections. We explored whether additional ECG criteria might help identify left-sided AV-connections. METHODS: We analyzed 156 patients who underwent an electrophysiology study (EPS) and ablation for paroxysmal supraventricular tachycardias (PSVT). Patients were divided into 2 groups: those with left-sided AV-connections (Group 1) and all other PSVT (Group 2). Various ECG parameters were compared before and after ablation in both groups. RESULTS: The EPS identified left-sided AV-connections among 43 patients (Group 1) and excluded it among 113 (Group 2). Baseline ECG in Group 1 demonstrated obvious preexcitation among 24/43 patients (55.8%), the remaining 19/43 missing obvious preexcitation. R/S ratio > 0.5 in V1 was noted in 38/43 (88.4%) patients in Group 1 before ablation (median 1.00; IQR 0.58-2.20), including 16/19 (84.2%) patients lacking obvious left-sided AVconnections. Conversely, only 10/113 (8.8%) patients in Group 2 had R/S ratios in V1 ≥ 0.5 (0.20; 0.10-0.31), P < 0.0001. After ablation, the R/S ratio decreased significantly in Group 1 (0.29; 0.17-0.45), P < 0.0001. Thus, a combined criterion of classic preexcitation or R/S ratio ≥ 0.5 on ECG identified 40/43 left-sided AV-connections (sensitivity 93.0%). The negative predictive value of this combined criterion was 103/106 (97.2%). CONCLUSIONS: In symptomatic patients, combining the R/S ratio (≥ 0.5) in lead V1 with the classic preexcitation pattern on ECG markedly improved the sensitivity to diagnose left-sided AV-connections. This ratio may be particularly useful among patients lacking obvious preexcitation.

Septal perforator anatomy and variability of perfusion bed by myocardial contrast echocardiography: a study of hypertrophic cardiomyopathy patients undergoing alcohol septal ablation.

OBJECTIVE: To characterize the perfusion bed of the first septal perforator by myocardial contrast echocardiography (MCE) in patients with hypertrophic cardiomyopathy undergoing alcohol septal ablation (ASA). BACKGROUND: MCE is used to define the septal perforator anatomy prior to ASA. Occasionally, ASA cannot be performed due to unfavorable septal anatomy or perfusion outside the interventricular septum. Despite the standard use of MCE for septal mapping, there are no reports describing the territory of septal perforator perfusion. METHODS: Forty-seven consecutive patients underwent ASA between 1/1/2004 and 12/30/2012. Blinded individuals retrospectively evaluated patients for septal perforator anatomic findings. Patients were divided into 2 groups based on presence or absence of extra-septal perfusion (ESP) as visualized by apical views after intracoronary contrast injection. The groups' procedural outcomes were compared, including infarct size, new conduction abnormalities, and major adverse events. RESULTS: Over 25% demonstrated ESP, of which 83% predominantly involved the right ventricular (RV) moderator band. The first septal perforator (FSP) was statistically larger in ostial diameter (1.69 mm vs. 1.23 mm, P = 0.04) and numerically more likely dominant in patients with ESP (63.6% vs. 47.2%, P = 0.22). In those with ESP, the odds ratio comparing FSP diameter of 2.0 mm to the mean was 1.96 (95% CI: 1.01-3.80). CONCLUSIONS: Downstream capillary perfusion may be discordant from epicardial territory and this study emphasizes the importance of MCE prior to ASA. Over 25% of our patients demonstrated ESP, most commonly involving the RV moderator band. The size of the FSP was the strongest predictor of ESP.