Acute and Chronic Sequelae of Ventricular Dyssynchrony

Extremely short setting of optimal sensed atrioventricular interval in patients after Fontan procedure with implanted dual-chamber pacemaker

BACKGROUND

Atrioventricular interval optimisation is important in patients with dual-chamber pacing, especially with heart failure. In patients with CHD, especially in those with Fontan circulation, the systemic atrial contraction is supposed to be more important than in patients without structural heart disease.

METHODS

We retrospectively evaluated two patients after Fontan procedure with dual-chamber pacemaker with a unique setting of optimal sensed atrioventricular interval.

RESULTS

The optimal sensed atrioventricular interval determined by echocardiogram was extremely short sensed atrioventricular interval at 25 and 30 ms in both cases; however, the actual P wave and ventricular pacing interval showed 180 and 140 ms, respectively. In both cases, the atrial epicardial leads were implanted on the opposite site of the origin of their own atrial rhythm. The time differences between sensed atrioventricular interval and actual P wave and ventricular pacing interval occurred because of the site of the epicardial atrial pacing leads and the intra-atrial conduction delay.

CONCLUSION

We need to consider the origin of the atrial rhythm, the site of the epicardial atrial lead, and the atrial conduction delay by using electrocardiogram and X-ray when we set the optimal sensed atrioventricular interval in complicated CHD.

How to improve outcomes: should we put more emphasis on programming and medical care and less on patient selection?

Many factors contribute to the pathophysiology and progression of heart failure (HF), offering the potential for many synergistic therapeutic approaches to its management. For patients, who have systolic HF, prolonged QRS and receiving guideline-indicated pharmacological therapy, cardiac resynchronization therapy (CRT) may provide additional benefits in terms of symptom improvement and mortality reduction. Nevertheless, in many patients, moderate or severe symptoms may persist or recur after CRT implantation due to either the severity or progression of the underlying disease, the presence of important co-morbidities or suboptimal device programming. Identifying and, where possible, treating the reasons for persistent or recurrent symptoms in patients who have received CRT is an important aspect of patient care. The present review summarizes the available evidence on this topic.

Influence of aetiology on long-term effects of resynchronization on cardiac structure and function in patients treated with β-blockers

OBJECTIVES

Cardiac resynchronization therapy (CRT) elicits more beneficial effects on left-ventricular (LV) structure and function, and long-term clinical outcomes in nonischemic heart failure patients. Rates of β-blocker use in recent heart failure trials are higher than in CRT trials and this may influence the response to CRT. This study examined the long-term effects of CRT on LV structure and function in New York Heart Association class III-IV β-blocker-treated patients.

METHODS

One hundred and four (41 ischemic and 63 nonischemic) CRT patients, who were receiving β-blockers before and throughout 12 months following device implantation, were retrospectively selected. Variations in echocardiographic parameters recorded before, and 6 and 12 months after CRT were analyzed.

RESULTS

Selected patients were all stable on β-blockers, angiotensin-converting enzyme inhibitors or angiotensin receptor blockers (97%) and diuretics (97%) before implantation. CRT was associated with significant improvements in LV morphological and systo-diastolic functional parameters at 6 months, with further improvements between 6 and 12 months seen in nonischemic patients only. Accordingly, rates of echocardiographic response to CRT were similar at 6 months but significantly higher in nonischemic patients after 1 year. The degree of reduction in LV diameters and volumes, and of increase in ejection fraction, was significantly larger in nonischemic patients at both 6 and 12 months. In addition, a significant reduction in LV mass and severity of mitral regurgitation was more evident in nonischemic patients both 6 and 12 months following CRT.

CONCLUSIONS

Ischemic aetiology of heart failure is associated with less favorable long-term effects of CRT on LV structure and function despite the systematic use of β-blockers.