Are changes in heart rate, observed during dobutamine stress echocardiography, associated with a response to cardiac resynchronisation therapy in patients with severe heart failure? Results of a multicentre ViaCRT study

According to current European Society of Cardiology guidelines for the diagnosis and treatment of heart failure (HF), cardiac resynchronisation therapy (CRT) is indicated in patients suffering from HF with reduced ejection fraction (EF) with significantly widened QRS complexes. The presence of vital myocardium proven by dobutamine stress echocardiography (DSE) is considered as a good prognostic factor for responsiveness to this treatment. Chronotropic incompetence is, on the other hand, a known factor of unfavourable outcome in HF. The aim of this study was to analyse the relationship between heart rate (HR) response during DSE and resultant changes in echocardiographic parameters determined prior to CRT and six weeks post-implantation of the CRT system. The study included 72 men and 25 women with chronic HF and markedly deteriorated left ventricular (LV) sys-tolic function (EF < 35%). Low-dose DSE was performed prior to the CRT system implantation. Baseline echocardiographic parameters determined before CRT were compared to those measured six weeks after implantation. Implantation of the CRT system resulted in an improvement of LV systolic function. DSE showed a significant in-crease in HR, by 16.3 bpm on average. Patients with the least prominent increase in HR during DSE (< 7 bpm) presented with significantly greater end-diastolic LV dimension and volume, as well as with significantly lower EF than the subjects with the most evident increase in HR (> 24 bpm). Improvement in EF at six weeks was associated with lower baseline HR and its greater absolute and relative increase during DSE. Greater absolute increase in HR during DSE was also associated with more prominent decrease in systolic/diastolic LV volumes. Patients with better chronotropic response during DSE show significant improvement in LV parameters determined by echocardiography within six weeks of CRT. Chronotropic response to pharmacologic stress test may serve as a predictive factor in patients qualified for CRT.