Ultrasonography evaluation of diaphragm kinetics in patients undergoing atrial fibrillation ablation with cryoballoon

Atrial fibrillation (AF) management is complex and includes both pharmacologic treatment and catheter ablation. Pulmonary vein isolation (PVI) is widely performed using cryoballoon (CB) technique. Among the complications, phrenic nerve paralysis (PNP), though rare, can occur during procedures due to the proximity of the phrenic nerve to the pulmonary veins. Even the subclinical damage can affect respiratory function, especially in those with comorbidities. This study aimed to assess the diaphragm kinetics using ultrasonographic parameters in patients undergoing PVI with CB.

A prospective, single-center observational study included 64 patients (44 AF ablation, 20 control) (mean age: 58.8 ± 10.6 years; 52% men). Diaphragm motion kinetics (DMK) were evaluated using Tissue Doppler (TDI) imaging for peak contraction and relaxation velocities (Figure 1A), as well as maximum displacement by M-mode imaging (Figure 1B), before and one hour after the procedure. Patients were monitored both clinically and with 48-hour Holter at 1-, 3-, 6-, 12-, 24-months post-procedure to assess a composite endpoint of recurrence, PNP, cardiac death and rehospitalization.

Patients in the AF ablation group had a high prevalence of hypertension (48%), dyslipidemia (37%), and heart failure (25%). All patients had paroxysmal AF. Baseline DMK values were similar between the AF and control groups (mean peak contraction TDI velocity: 5.1 ± 0.7 vs. 5.0 ± 0.9, p=0.470; mean peak relaxation TDI velocity: 4.7 ± 1.0 vs. 4.7 ±1.1, p=0.899). Median total CB duration was 840 (IQR 800-946) minutes with a mean cooling degree of -44 degrees per pulmonary vein. Acute procedural success was achieved in all cases. Postprocedural DMK values were significantly lower than preprocedural DMK (mean peak contraction TDI velocity: 5.0 ± 0.9 vs. 3.5 ± 1.2 cm/s, p<0.001; mean peak relaxation TDI velocity: 4.7 ± 1.0 vs. 3.4 ±1.2 cm/s, p<0.001; mean M mode displacement: 46.1 ± 9.9 vs. 30.8 ± 11.4, p<0.001). (Figure 2) Subclinical DMK abnormalities were seen in 33 (78.5%) of cases. Two patients (4.5%) developed PNP; both were treated conservatively and showed improvement during follow-up. During a mean follow-up duration of 18 months, composite outcomes were observed in 13 (29.5%) patients, primarily due to AF recurrence (22.7%), followed by cardiac death (9.1%).

Subclinical diaphragm kinetic abnormalities are frequently observed and can be effectively measured using TDI and M-mode techniques in patients undergoing PVI with CB. However, these abnormalities did not lead to an increase in composite adverse outcomes.Figure 1  Figure 2