{'fraction_non_alphanumeric': 0.030004688232536336, 'fraction_numerical': 0.02390998593530239, 'mean_word_length': 5.258064516129032, 'pattern_counts': {'":': 0, '<': 1, '<?xml version=': 0, '>': 1, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Multi-chamber pacing: a perfect solution for cardiac mechanical dyssynchrony?

See doi:10.1016/S1095-668X(02)00475-Xfor the article to which this editorial refers. 

When the heart fails, it becomes less efficient, as myocardial energy consumption rises without a corresponding increase in cardiac output. There are many possible reasons for this decline in cardiac efficiency (Fig. 1). Recently, because of the potential value of multi-site pacing, interest has focused on mechanical dyssynchrony, which encompasses a complex array of problems that often coexist in varying degrees along with ‘functional’ mitral regurgitation.1–3



 Fig. 1 
Some mechanisms of heart failure causation and progression (usually multiple mechanisms operating simultaneously conspire to cause progression of heart failure).



It is likely that mechanical dyssynchrony is common, although precisely how common is unclear, and will depend on the definition and the tools used to measure it. The presence and severity of cardiac dyssynchrony can be assessed directly using imaging techniques or indirectly by measuring time-intervals from a standard 12-lead echocardiography (ECG). ECG is the current method of choice owing to its wide availability, high temporal resolution and its ability to assess flow across the valves, although diagnostic criteria for cardiac dyssynchrony are still being refined.4 In the meantime, studies on relatively small numbers of patients have suggested that patients who have a QRS width ≥150ms very often have evidence of major inter- and intra-ventricular dyssynchrony on imaging.5 A high, but as yet uncertain, proportion of patients with QRS 120–150ms will also fulfil current echocardiographic criteria for ventricular dyssynchrony.6,7 Approximately, one in every four patients with heart failure secondary to left ventricular systolic dysfunction (LVSD) will have a QRS width >120ms on their surface ECG.8 The PR interval may be a useful marker for atrio-ventricular dyssynchrony,1 but <5% of patients with heart failure and LVSD will have a PR interval ≥220ms.8–11

Mechanical dyssynchrony and the possibility of …