sirtuin inhibitors ICE was introduced as a
ICE was introduced as a real-time imaging technique to assist catheter ablation procedures. Chu et al. performed an ICE-guided catheter ablation in 9 dogs. They concluded that ICE can accurately guide catheter ablation directed at anatomic landmarks. They also used ICE to confirm the endocardial contact, identify electrode movement, and directly visualize lesions .
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Introduction Current guidelines offer clear boundaries for cardiac resynchronization therapy (CRT) . However, clinicians are often presented with patients, who although they fall just outside the boundaries for guideline-driven therapy, present with certain clinical characteristics that suggest that they would benefit from treatment. Herein, we describe one such case.
Case report A 55 year-old female with a long-standing history of left bundle branch block (LBBB), hypertension and hyperlipidemia presented for evaluation of 4 years of progressive dyspnea on exertion. On evaluation, she endorsed New York Heart Association (NYHA) Class III sirtuin inhibitors failure symptoms despite being on an optimal medical regimen (beta-blocker and angiotensin receptor blocker at maximally tolerated doses). She described marked dyspnea with lifting, climbing stairs or walking short distances. The electrocardiogram revealed sinus bradycardia at a rate of 48 beats per minute with a complete LBBB (QRS duration of 150ms). (Fig. 1(a)) The coronary angiogram from an outside institution revealed normal coronary arteries. A trans-thoracic echocardiogram revealed mild left ventricular systolic dysfunction with a low-normal ejection fraction (EF) of 50%, stage-two diastolic dysfunction, and moderate mitral regurgitation with a structurally normal valve at rest. Significant ventricular dyssynchrony was present at rest based on: (1) intraventricular mechanical delay: (a) mean time-to-peak myocardial velocity of 255.83ms (standard deviation 52.13ms, cut-off is ≥33ms), (b) greatest intraventricular delay (time to peak velocity difference) – posterior base: 110ms (cut-off is >100ms), and (c) aortic pre-ejection time of 150ms (cut-off is ≥140ms); and (2) interventricular mechanical delay of 60ms (cut-off is ≥40ms). However the exercise stress echocardiogram demonstrated a decrease in left ventricular ejection fraction with exercise to 30%, with an increase in mitral regurgitation from moderate to severe as well as an increase in right ventricular systolic pressure from 27 to 60mmHg although the QRS width did not increase with exercise. The functional capacity was 5.7 metabolic equivalents (METS) (stage 2 Bruce protocol), reaching a heart rate of 157 beats per minute (95% maximal predicted heart rate) with an exercise duration of 4min. Since the mitral valve was structurally normal, it was felt that mitral valve repair was not indicated, and given her debilitating symptoms, in the setting of a baseline left bundle branch block with documented dyssynchrony, she was offered a bi-ventricular pacemaker. We hoped to improve her ventricular synchrony and left ventricular function, particularly during exertion. A bi-ventricular pacemaker and not an ICD was placed without complications following the patient׳s consent since the resting EF was 50%. Her paced electrocardiogram is demonstrated in Fig. 1(b). At one-year follow-up, she endorsed a dramatic improvement in her exercise capacity with NYHA Class II symptoms with the ability to pick up her grandchild, walk up one flight of stairs and walk on level ground at a regular pace. A follow-up exercise echocardiogram demonstrated reduction in resting mitral regurgitation to mild both at rest and during exertion as well as a improvement in her right ventricular systolic pressure with exercise to 42mmHg (see Fig. 2(a) and (b) for representative flow velocity across the tricuspid valve with exercise pre- and post-device placement). There was also an improvement in the resting EF to >55% that was maintained during exercise with an improved functional capacity on her repeat treadmill stress echocardiogram with a functional capacity of 7 METS (stage 3 Cornell protocol), 6min exercise duration and peak heart rate of 134 beats per minute (84% maximal predicted heart rate). Her device was programed DDD 50-140.