Predictors for cardiac resynchronization therapy response: the importance of QRS morphology and left ventricular lead position

Cardiac resynchronization therapy and its role in the management of heart failure

The prevalence of heart failure is increasing and it is associated with significant mortality and morbidity. Optimal medical therapy improves outcome, but heart failure continues to have a substantial impact on both the individual patient and wider society. Over the last two decades, cardiac resynchronization therapy has revolutionized the treatment of selected patients who have heart failure. Cardiac resynchronization therapy significantly reduces mortality and hospitalization through reverse cardiac remodelling. This review informs non-specialists about cardiac resynchronization therapy and for which patients it should be considered.

Treatment of Heart Failure With Reduced Ejection Fraction-Recent Developments

Heart failure with reduced ejection fraction (HFrEF) represents at least half of the cases of heart failure, which is a syndrome defined as the inability of the heart to supply the body's tissues with an adequate amount of blood under conditions of normal cardiac filling pressure. HFrEF is responsible for high costs and rates of mortality, morbidity, and hospital admissions, mainly in developed countries. Thus, the need for better diagnostic methods and therapeutic approaches and consequently better outcomes is clear. In this article, we review the principal aspects of pathophysiology and diagnosis of HFrEF, with focus on emerging biomarkers and on recent echocardiographic methods for the assessment of left ventricular function. Furthermore, we discuss several major developments in pharmacological and nonpharmacological treatment of HFrEF in the last years, including cardiac resynchronization therapy, implantable cardioverter defibrillators, and the recent and promising drug LCZ696, focusing on current indications, unanswered questions, and other relevant aspects.

Prognostic Role of Right Ventricular Function in Patients With Heart Failure Undergoing Cardiac Resynchronization Therapy

BACKGROUND

Because 20% to 40% of patients undergoing cardiac resynchronization therapy (CRT) do not respond to it, identification of potential factors predicting response is a relevant research topic.

HYPOTHESIS

There is a possible association between right ventricular function and response to CRT.

METHODS

We analyzed 227 patients from the Cardiac Resynchronization Therapy Modular Registry (CRT-MORE) who received CRT according to current guidelines from March to December 2013. Response to therapy was defined as a decrease of ≥15% in left ventricular end-systolic volume (LVESV) at 6 months.

RESULTS

The tricuspid annular plane systolic excursion (TAPSE) value that best predicted improvement in LVESV (sensitivity 68%, specificity 54%) was 17 mm. Stratifying patients according to TAPSE, LVESV decreased ≥15% in 78% of patients with TAPSE >17 mm (vs 59% in patients with TAPSE ≤17 mm; P = 0.006). At multivariate analysis, TAPSE >17 mm was independently associated with LVESV improvement (odds ratio: 1.97, 95% confidence interval: 1.03-3.80, P < 0.05), together with ischemic etiology (odds ratio: 0.39, 95% confidence interval: 0.20-0.75, P < 0.01). These results were confirmed for New York Heart Association class III to IV patients (79% echocardiographic response rate in patients with TAPSE >17 mm vs 55% in patients with TAPSE <17 mm; P = 0.012).

CONCLUSIONS

Baseline signs of right ventricular dysfunction suggest possible remodeling after CRT. A TAPSE value of 17 mm was identified as a good cutoff for predicting a better response to CRT in patients with both mildly symptomatic and severe heart failure.

A Case of Useful Short-Spaced Bipolar Pacing of a Left Ventricular Lead to Avoid Phrenic Nerve Stimulation

A 48-year-old woman underwent cardiac resynchronization therapy defibrillator implantation. Coronary sinus (CS) venography showed only one adequate anterior branch for a left ventricular lead. We were able to introduce a quadripolar left ventricular lead (Medtronic 4398-88 cm) to the distal portion of the anterior branch. Although phrenic nerve stimulation (PNS) occurred due to distal bipolar pacing (distal 1-mid 2, with 21-mm distance) and proximal pacing (mid 3-proximal 4, distance 21mm), short-spaced bipolar pacing (mid 2-3, distance 1.3 mm) did not induce PNS until 9V pacing. Shared bipolar pacing from each left ventricular electrode (distal 1 to proximal 4) as cathode and a right ventricular (RV) coil as anode resulted in PNS by 3.0V at 0.4 ms. Although quadripolar pacing could avoid PNS by switching the pacing site (ie, from distal bipolar to proximal bipolar), it might not avoid PNS in cases where the phrenic nerve and CS branch are parallel and in close proximity. We found that even though the phrenic nerve and CS branch were parallel and close, short-spaced bipolar pacing could avoid PNS. In conclusion, short-spaced bipolar pacing selected by quadripolar pacing might be beneficial to avoid PNS when the implantable branch is limited.

Effects of Cardiac Resynchronization Therapy on Ventricular Electrical Remodeling in Patients With Heart Failure

Cardiac resynchronization therapy (CRT) reverses structural remodeling of the left ventricle. We investigated whether CRT reverses left-ventricular electrical remodeling.Eighty patients were enrolled and implanted with CRT-devices. Echocardiography and electrocardiography data were obtained from each patient prior to implantation and two years after implantation. At two years after implantation, the patients were classified into a responder group and a non-responder group based on echocardiography.Over the next 2 years, 75 patients completed follow-up, and 5 patients had died. Echocardiography results showed that 23 patients could be classified as non-responders and 52 as responders. Larger numbers of non-responders were diagnosed with either ischemic cardiomyopathy (ICM) or nonspecific intraventricular conduction delay (NICD). The intrinsic QRS duration was not changed in responders, patients with dilated cardiomyopathy, or in the patient categories of male and female. However, the intrinsic QRS duration was significantly prolonged in non-responders and patients with ischemic cardiomyopathy (P = 0.041). The mean left ventricular end-diastolic diameter in the responder group was significantly decreased by CRT (P < 0.05), while there was no significant change in intrinsic QRS duration.While CRT does not reduce the intrinsic QRS duration, it can delay negative ventricular electrical remodeling. Continuous CRT is necessary.