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Background and Objectives: Cardiac Resynchronization Therapy (CRT) has, besides its benefits, various limitations. For instance, atrial fibrillation (AF) has a huge impact on the therapy efficacy. It usually reduces the overall BiV pacing percentage and leads, inevitably, to lack of fusion beats. In many patients with heart failure that could benefit from resynchronization, the QRS morphology is often IVCD and atypical, or non-LBBB, which further diminishes the CRT response. In those cases, we established His pacing combined with LV pacing as a feasible option to reduce the impact of AF on the CRT response and regain partially physiological ventricular activation to improve the electromechanical sequence. Materials and Methods: We implanted two patients with AF, HF, EF < 35%, NYHA II-III and QRS > 150 ms with CRT-D systems modified to HOT-CRT and observed their clinical, ECG and echocardiographic improvements over a follow-up period of three months. Results: In both patients we observed improvements of the initial parameters. We were able to shorten the QRS duration to approx. 120 ms, improve NYHA functional class, increase the EF by approximately 12% and distinctly reduce mitral regurgitation. Conclusion: Since the conventional CRT reaches its limits within this specific patient group, we need to consider alternative pacing sites and the effective combination of them. Our results and respectively other studies that are also mentioned in the current guidelines, support the feasibility of HOT-CRT in the above mentioned patient group.

Functional and structural changes in atrial muscle constitute a substrate for atrial fibrillation. The pathological changes in the left atrium decrease conduction velocity and result in prolongation of the P wave duration. The aim of the study was to assess the duration of the P wave in patients with paroxysmal and persistent atrial fibrillation. The study group consisted of 119 patients diagnosed with atrial fibrillation, 57 women and 62 men, aged 65.3+/-9.4 years. There were 65 patients with paroxysmal AF and 54 with persistent AF. In this group the electrical cardioversion was performed. The P wave duration, was measured using electrophysiological system in all leads at paper speed of 200 mm/s. The studied patients did not differ in term of age, gender and comorbidities. The patients with persistent AF had longer P wave duration (159.9+/-22.3 vs 144.6+/-17.2 ms, p<0.001), higher glucose concentration (119.4+/-33.4 vs 108.0+/-24.6 mg/dL, p=0.015). Those results were not influenced by the anti-arrhythmic treatment. The persistent atrial fibrillation shows prolongation of the P wave duration over the paroxysmal form of the arrhythmia, independently to age, gender and anti-arrhythmic medication. The prolongation of the P wave related to persistent arrhythmia should force the physicians to earlier restoration of the sinus rhythm in order to its more successful long term maintenance.

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