Imaging techniques in cardiac resynchronization therapy

Abstract

Cardiac resynchronization therapy is a high cost therapeutic option with proven efficacy on improving symptoms of ventricular failure and for reducing both hospitalization and mortality. However, a significant number of patients do not respond to cardiac resynchronization therapy that is due to various reasons. Identification of the optimal pacing site is crucial to obtain the best therapeutic result that necessitates careful patient selection. Currently, using echocardiography for mechanical dyssynchrony assessment performs patient selection. Multi-Detector-Row Computed Tomography (MDCT) and Magnetic Resonance Imaging (MRI) are new imaging techniques that may assist the cardiologist in patient selection. These new imaging techniques have the potential to improve the success rate of cardiac resynchronization therapy, due to pre-interventional evaluation of the venous coronary anatomy, to evaluation of the presence of scar tissue, and to improved evaluation of mechanical dyssynchrony. In conclusion, clinical issues associated with heart failure in potential candidates for cardiac resynchronization therapy, and the information regarding this therapy that can be provided by the imaging techniques echocardiography, MDCT, and MRI, are reviewed.

Fig. 1

Two-dimensional echocardiographic image of a sixty three years old male, candidate to cardiac resynchronization therapy, presenting interventricular dyssynchrony shown by interventricular mechanical delay with a difference between the (a) aortic pre-ejection time and (b) pulmonar pre-ejection time, which was >40 ms

Fig. 2

Echocardiographic image of a sixty eight years old female, candidate to cardiac resynchronization therapy, showing a post-systolic contraction or delayed activation of lateral wall (co-existence of systole and diastole), measured by overlap of the LV lateral wall contraction (by using M-mode) and onset of diastolic filling (by using transmitral Doppler E-wave onset)

Fig. 3

M-mode echocardiographic image of a fifty three years old female, candidate to cardiac resynchronization therapy, showing septal-to-posterior wall motion delay (>140 ms).

Fig. 4

Tissue Doppler Image echocardiography of 74-years-old male, candidate to cardiac resynchronization therapy, showing mechanical delay between (a) the interventricular septum and (b) the lateral left ventricular wall, that was >65 ms

Fig. 5

Multi-detector computed tomography coronary angiography acquired with 0.5 mm collimation and half-scan reconstruction (Toshiba Aquilion 64 CT-scanner) in a 66-years-old male patient showing normal coronary arteries (a) and in a sixty six years old male patient showing coronary artery disease (b). The left anterior descending (LAD) coronary artery and a diagonal branch (D) are visualized in both patients. Note the irregular lumen of the LAD that was heavily calcified in the patient with coronary artery disease (b). Curved multiplanar reconstructions of the diseased LAD that displays the artery in a single image is shown in two perpendicular longitudinal directions

Fig. 6

Multi-detector computed tomography angiography (0.5 mm collimation and half-scan reconstruction, sixty six years old male patient). Volume rendering images showing the coronary venous system. CS = coronary sinus; GCV = great cardiac vein; AIV = anterior interventricular vein; LMV = left marginal vein; PIV = posterior interventricular vein; OM = obtuse marginal coronary artery branch; RCA = right coronary artery

Fig. 7

Magnetic resonance imaging in a 20-year-old healthy male. Short-axis images at left midventricular level. Functional imaging (balanced turbo field-echo sequence with TR 3.8 ms, TE 1.9 ms, flip angle 70°, slice thickness 8 mm) at end-diastolic (a) and end-systolic (b) time points. Note the equal circular contraction of the left ventricular wall. Ejection fraction was 60%

Fig. 8

Magnetic resonance imaging in a 22-years-old healthy male. Short-axis tagging imaging at left midventricular level with echo-planar imaging (EPI) tagging sequence with EPI factor 7, TR 30 ms, TE 13 ms, flip angle 20°, slice thickness 8 mm, at end-diastolic (a) and end-systolic (b) time points. Vector motion analysis of tagging points throughout the cardiac cycle allows left ventricular strain rate analysis

Fig. 9

Example of flow velocity reconstruction through the mitral valve plane from 3-directional velocity-encoded MRI. During systole, the regurgitant jet is clearly presented. During diastole, the inflow is visualized

Fig. 10

Example of LV dyssynchrony measurements in a healthy volunteer (A,B) and a patient with extensive dyssynchrony (C, D). In A and C, the longitudinal velocities measured with MRI are presented. Sample volumes are placed in septal and lateral wall at the basal level. The mean velocities measured in these sample volumes are presented in B and C. In B, the peak systolic velocities of septal and lateral wall coincide. In D, a large delay between peak systolic velocities in septal and lateral wall of 115 ms is present

Fig. 11

Magnetic resonance imaging in a 65-years-old female who had a myocardial infarction in the past. Short-axis images at left midventricular level. Delayed enhancement technique (T1-weighted turbo-field echo sequence with turbo factor 40 and TR 3.9 ms, TE 12 ms, flip angle 15°, slice thickness 10 mm) 17 min following gadolinium-chelate administration showing delayed enhancement as sign of scar tissue in the inferior wall regions (a). Functional imaging (balanced turbo field-echo sequence with TR 3.8 ms, TE 1.9 ms, flip angle 70°, slice thickness 8 mm) at end-diastolic (b) and end-systolic (c) time points. Note the lack of wall thickening in the inferior wall regions that corresponds to the area of delayed enhancement. Ejection fraction was 36%