Therapy Of Cardiac Arrhythmias In Children: An Emerging Role Of Electroanatomical Mapping Systems

Spectral Analysis of Tissue Displacement for Cardiac Activation Mapping: Ex Vivo Working Heart and In Vivo Study

Characterizing myocardial activation is of major interest for understanding the underlying mechanism of cardiac arrhythmias. Electromechanical wave imaging (EWI) is an ultrafast ultrasound-based method used to map the propagation of the local contraction triggered by electrical activation of the heart. This study introduces a novel way to characterize cardiac activation based on the time evolution of the instantaneous frequency content of the cardiac tissue displacement curves. The first validation of this method was performed on an ex vivo dataset of 36 acquisitions acquired from two working heart models in paced rhythms. It was shown that the activation mapping described by spectral analysis of interframe displacement is similar to the standard EWI method based on zero-crossing of interframe strain. An average median error of 3.3 ms was found in the ex vivo dataset between the activation maps obtained with the two methods. The feasibility of mapping cardiac activation by EWI was then investigated on two open-chest pigs during sinus and paced rhythms in a pilot trial of cardiac mapping with an intracardiac probe. Seventy-five acquisitions were performed with reasonable stability and analyzed with the novel algorithm to map cardiac contraction propagation in the left ventricle (LV). Sixty-one qualitatively continuous isochrones were successfully computed based on this method. The region of contraction onset was coherently described while pacing in the imaging plane. These findings highlight the potential of implementing EWI acquisition on intracardiac probes and emphasize the benefit of performing short time-frequency analysis of displacement data to characterize cardiac activation in vivo.

Effects of Sacubitril/Valsartan in Patients with High Arrhythmic Risk and an ICD: A Longitudinal Study

PURPOSE

Patients affected by heart failure with reduced ejection fraction (HFrEF) receive clinical and functional beneficial effects from treatment with sacubitril/valsartan. However previous studies have shown that patients with an implantable cardioverter defibrillator (ICD) could obtain even greater benefit, but only make up a only a small proportion of patients. In the current study we evaluated the effect of sacubitril/valsartan in patients with an ICD.

METHODS

Thirty-five outpatients with HFrEF (aged 60 ± 11 years, 28 were males), on optimal medical therapy were studied. All patients received an ICD at least 6 months before enrollment or were non-responders to ICD plus resynchronization (CRT-D). An open-label sacubitril/valsartan treatment was established at the maximum tolerated dose. Clinical assessment, 6-min walk test (6MWT) and echocardiography, were performed during follow-up at 90, 180, and 360 days. Quality of life score and perceived fatigue on exercise were assessed.

RESULTS

Clinical conditions dramatically improved in most patients, especially within the first 6 months of therapy (76 % were in NYHA-I and 24 % in NYHA-II at the end of study vs 71 % NYHA-II and 29 % NYHA III at enrollment, p < 0.001). Quality of life and exercise performance significantly improved according to N-terminal pro-brain natriuretic peptide (NT-proBNP) serum levels lowering. Walking distance at 6MWT increased from 274 ± 97 to 389 ± 53 m and walking speed from 0.74 ± 0.27 to 1.07 ± 0.15 m/s (p < 0.001), while oxygen saturation did not differ significantly (from 90 ± 1 % to 91 ± 2 %). More gradual was left ventricular reverse remodeling. Ejection fraction improved mildly (+ 5 points %, p < 0.001). Global longitudinal strain and diastolic function were also assessed over time.

CONCLUSION

Sacubitril/valsartan therapy for HFrEF may lead to significant clinical and functional improvements even in patients with ICD at greater arrhythmic risk. Clinical improvement is obtained within the first 6 months of treatment while reverse remodeling needs more time.