Characteristics of the electrocardiogram in patients with continuous-flow left ventricular assist devices

BACKGROUND

Electrocardiograms (ECGs) are routinely obtained in patients with advanced congestive heart failure (CHF) before and after surgical implantation with a left-ventricular assist device (LVAD). As the number of patients with CHF is increasing, it is necessary to characterize the changes present in the ECG of patients with LVADs.

METHODS

ECGs of 43 patients pre- and postimplantation of a HeartMate II LVAD were compared to characterize the presence of an LVAD using the following six criteria (LVADS2 ): low limb-lead voltage, ventricular pacing, artifact (electrical), duration of the QRS > 120 milliseconds, ST-elevation in the lateral leads, and splintering of the QRS complex. Additionally, 50 ECGs of non-LVAD patients coded as "lateral myocardial infarction (MI)" and 50 ECGs coded as "ventricular pacing" were chosen at random and scored. Odds ratios were calculated using Fisher's exact test. Logistic regression models were built to predict the presence of an LVAD in all patients.

RESULTS

Univariate analysis of the pre- and post-LVAD ECGs confirmed that all criteria except the "Duration of QRS > 120 milliseconds" characterized the ECG of a patient with an LVAD. Electrical artifact and low limb-lead voltage yielded the greatest association with an LVAD-ECG.

CONCLUSIONS

The ECG of a patient with end-stage CHF significantly changes with LVAD implantation. The LVADS2 criteria provide a framework towards characterizing and establishing a new baseline of the ECG in a patient with a continuous-flow LVAD.

Strategies to improve cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) emerged 2 decades ago as a useful form of device therapy for heart failure associated with abnormal ventricular conduction, indicated by a wide QRS complex. In this Review, we present insights into how to achieve the greatest benefits with this pacemaker therapy. Outcomes from CRT can be improved by appropriate patient selection, careful positioning of right and left ventricular pacing electrodes, and optimal timing of electrode stimulation. Left bundle branch block (LBBB), which can be detected on an electrocardiogram, is the predominant substrate for CRT, and patients with this conduction abnormality yield the most benefit. However, other features, such as QRS morphology, mechanical dyssynchrony, myocardial scarring, and the aetiology of heart failure, might also determine the benefit of CRT. No single left ventricular pacing site suits all patients, but a late-activated site, during either the intrinsic LBBB rhythm or right ventricular pacing, should be selected. Positioning the lead inside a scarred region substantially impairs outcomes. Optimization of stimulation intervals improves cardiac pump function in the short term, but CRT procedures must become easier and more reliable, perhaps with the use of electrocardiographic measures, to improve long-term outcomes.

Determination of the longest intrapatient left ventricular electrical delay may predict acute hemodynamic improvement in patients after cardiac resynchronization therapy

BACKGROUND

One of the reasons for patient nonresponse to cardiac resynchronization therapy is a suboptimal left ventricular (LV) pacing site. LV electric delay (Q-LV interval) has been indicated as a prognostic parameter of cardiac resynchronization therapy response. This study evaluates the LV delay for the optimization of the LV pacing site.

METHODS AND RESULTS

Thirty-two consecutive patients (23 men; mean age, 71±11 years; LV ejection fraction, 30±6%; 18 with ischemic cardiomyopathy; QRS, 181±25 ms; all mean±SD) underwent cardiac resynchronization therapy device implantation. All available tributary veins of the coronary sinus were tested, and the Q-LV interval was measured at each pacing site. The hemodynamic effects of pacing at different sites were evaluated by invasive measurement of LV dP/dtmax at baseline and during pacing. Overall, 2.9±0.8 different veins and 6.4±2.3 pacing sites were tested. In 31 of 32 (96.8%) patients, the highest LV dP/dtmax coincided with the maximum Q-LV interval. Q-LV interval correlated with the increase in LV dP/dtmax in all patients at each site (AR1 ρ=0.98; P<0.001). A Q-LV value >95 ms corresponded to a >10% in LV dP/dtmax. An inverse correlation between paced QRS duration and improvement in LV dP/dtmax was seen in 24 patients (75%).

CONCLUSIONS

Pacing the LV at the latest activated site is highly predictive of the maximum increase in contractility, expressed as LV dP/dtmax. A positive correlation between Q-LV interval and hemodynamic improvement was found in all patients at every pacing site, a value of 95 ms corresponding to an increase in LV dP/dtmax of ≥10%.

The ARCHITECT galectin-3 assay: comparison with other automated and manual assays for the measurement of circulating galectin-3 levels in heart failure

Heart failure (HF) is a common disease and affects millions of patients worldwide. Diagnosis, risk assessment and treatment of HF are difficult and therefore there is a need for additional tools to improve clinical performance. Biomarkers may be helpful in this respect. Galectin-3 is a relatively new biomarker that has been shown to have strong associations with the development of HF. Galectin-3 plays a role in inflammation and fibrosis, which are key elements in the pathophysiology of HF. Circulating plasma or serum galectin-3 levels have strong associations with the severity of HF and may be used to prognosticate or risk-stratify HF patients. Currently, there are several commercially available assays that can measure circulating galectin-3. This article describes the role galectin-3 plays in HF and its prognostic consequences. We will summarize the technical specifications of various manual and automated galectin-3 assays, which may help in HF management.