Recent advances in cardiac resynchronization therapy: echocardiographic modalities, patient selection, optimization, non-responders—all you need to know for more efficient CRT

Clinical assessment of intraventricular blood transport in patients undergoing cardiac resynchronization therapy

In the healthy heart, left ventricular (LV) filling generates different flow patterns which have been proposed to optimize blood transport by coupling diastole and systole. This work presents a novel image-based method to assess how different flow patterns influence LV blood transport in patients undergoing cardiac resynchronization therapy (CRT). Our approach is based on solving the advection equation for a passive scalar field from time-resolved blood velocity fields. Imposing time-varying inflow boundary conditions for the scalar field provides a straightforward method to distinctly track the transport of blood entering the LV in the different filling waves of a given cardiac cycle, as well as the transport barriers which couple filling and ejection. We applied this method to analyze flow transport in a group of patients with implanted CRT devices and a group of healthy volunteers. Velocity fields were obtained using echocardiographic color Doppler velocimetry, which provides two-dimensional time-resolved flow maps in the apical long axis three-chamber view of the LV. In the patients under CRT, the device programming was varied to analyze flow transport under different values of the atrioventricular conduction delay, and to model tachycardia (100 bpm). Using this method, we show how CRT influences the transit of blood inside the left ventricle, contributes to conserving kinetic energy, and favors the generation of hemodynamic forces that accelerate blood in the direction of the LV outflow tract. These novel aspects of ventricular function are clinically accessible by quantitative analysis of color-Doppler echocardiograms.

Normality index of ventricular contraction based on a statistical model from FADS

Radionuclide-based imaging is an alternative to evaluate ventricular function and synchrony and may be used as a tool for the identification of patients that could benefit from cardiac resynchronization therapy (CRT). In a previous work, we used Factor Analysis of Dynamic Structures (FADS) to analyze the contribution and spatial distribution of the 3 most significant factors (3-MSF) present in a dynamic series of equilibrium radionuclide angiography images. In this work, a probability density function model of the 3-MSF extracted from FADS for a control group is presented; also an index, based on the likelihood between the control group's contraction model and a sample of normal subjects is proposed. This normality index was compared with those computed for two cardiopathic populations, satisfying the clinical criteria to be considered as candidates for a CRT. The proposed normality index provides a measure, consistent with the phase analysis currently used in clinical environment, sensitive enough to show contraction differences between normal and abnormal groups, which suggests that it can be related to the degree of severity in the ventricular contraction dyssynchrony, and therefore shows promise as a follow-up procedure for patients under CRT.

Long-term clinical effects of programmer-guided atrioventricular and interventricular delay optimization: Intracardiac electrography versus echocardiography for cardiac resynchronization therapy in patients with heart failure

Objectives

To compare the haemodynamic results and long-term clinical outcomes of intracardiac electrography (QuickOpt®; St Jude Medical, St Paul, MN, USA) and echocardiography for optimization of atrioventricular (AV) and interventricular (VV) delays in cardiac resynchronization therapy (CRT).

Methods

Patients with CRT devices were prospectively enrolled; AV/VV delays were optimized by either QuickOpt® or echocardiography. Patients in the QuickOpt® group underwent both echocardiography and QuickOpt® optimization, and QuickOpt® AV/VV delays were used to program the CRT. All patients were followed-up for 12 months.

Results

In total, 44 patients were enrolled. There was good correlation between AV/VV delays determined by QuickOpt® ( n = 20) and echocardiography ( n = 24). QuickOpt® was significantly faster than echocardiography-guided optimization. Cardiac function, 6-min walking distance and left ventricular ejection fraction were significantly and similarly improved in both groups at 6 and 12 months compared with baseline. In the QuickOpt® group, left ventricular end diastolic diameters were significantly smaller at 6 and 12 months compared with baseline.

Conclusions

QuickOpt® is a quick, convenient and easy to perform method for optimization of AV and VV delays, with a similar long-term clinical outcome to echocardiography-guided optimization.

Heart failure patients selection for cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) is an established treatment for refractory chronic heart failure (CHF) patients with ventricular dyssynchrony. The patient selection for this therapy remains the basis for response improvement. Various parameters, methods and technology for identification of appropriate patient are under research. The influences of age and gender, disease progress stage such as mild and late stage CHF including right ventricular dysfunction, dyssynchrony and scar identified by imaging techniques like echocardiography, magnetic resonance and nuclear imaging, and atrial fibrillation on CRT benefits were respectively discussed. This review summarizes the current advancement in these areas.

Echocardiography as a guidance in CRT management: the GPS system in a labyrinth?

Although progress has been made to understand the factors for non-responsiveness, fine tuning and comprehensive strategies are needed to make echocardiography the GPS system in cardiac resynchronization. Taking the wrong turn in the labyrinth of dyssynchrony is expensive and time consuming without improving well being of the heart failure patient. Possibly other imaging techniques could help in fine tuning cardiac resynchronization.