Use of left ventricular pacing in heart failure: evaluation by gated blood pool imaging

Value of mechanical dyssynchrony as assessed by radionuclide ventriculography to predict the cardiac resynchronization therapy response

AIMS

To assess the value of mechanical dyssynchrony measured by equilibrium radionuclide angiography (ERNA) in predicting long-term outcome in cardiac resynchronization therapy (CRT) patients.

METHODS AND RESULTS

We reviewed 146 ERNA studies performed in heart failure patients between 2001 and 2011 at our institution. Long-term follow-up focused on death from any cause or heart transplantation. Phase images were computed using the first harmonic Fourier transform. Intra-ventricular dyssynchrony was calculated as the delay between the earliest and most delayed 20% of the left ventricular (LV) (IntraV-20/80) and inter-ventricular dyssynchrony as the difference between LV- and right ventricular (RV)-mode phase angles (InterV). Eighty-three patients (57%) were implanted with a CRT device after ERNA. Median follow-up was 35 [21-50] months. Twenty-four events were observed during the first 41 months. Median baseline ERNA dyssynchrony values were 28 [3 to 46] degrees for intraV-20/80 and 9 [-6 to 24] degrees for interV. Comparing survival between CRT and non-CRT patients according to dyssynchrony status, log-rank tests showed no difference in survival in patients with no ERNA dyssynchrony (P = 0.34) while a significant difference was observed in ERNA patients with high level of mechanical dyssynchrony (P = 0.004).

CONCLUSION

ERNA mechanical dyssynchrony could be of value in CRT patient selection.

Quantification of ventricular resynchronization reserve by radionuclide phase analysis in heart failure patients: a prospective long-term study

BACKGROUND

Phase analysis, developed to assess dyssynchrony from ECG-gated radionuclide ventriculography, has shown promising results. We hypothesized that quantifying the cardiac resynchronization reserve, that is, the extent of response to cardiac resynchronization therapy (CRT), by radionuclide imaging could potentially identify patients who are best suited for CRT.

METHODS AND RESULTS

Seventy-four patients ages 64.8±10.1 years were prospectively studied from July 2004 to July 2006, of whom 62.2% and 37.8%, respectively, were in New York Heart Association class 3 and 4. Mean QRS width was 173±25 ms. ECG-gated radionuclide ventriculography to quantify interventricular and intraventricular dyssynchrony was performed at baseline with and without CRT and at the 3-month follow-up visit. Amino-terminal-pro-brain natriuretic peptide (NT-pro-BNP) levels were also determined at baseline and at 3 months. During a mean follow-up of 10.1±7.6 months, there were 37 (50%) clinical events that defined the nonresponder group, including cardiac death or readmission for worsening heart failure. In multivariate Cox model analysis, higher NT-pro-BNP blood levels were associated with a significant increase in the risk for event (hazard ratio=1.085 for a 100 pg/L increase in NT-pro-BNP; 95% confidence interval, 1.014 to 1.161). Each 10° elevation in intraventricular dyssynchrony was associated with a decrease in the risk of events (hazard ratio=0.456, 95% confidence interval, 0.304 to 0.683). Receiver operating characteristic curve analysis demonstrated that an interventricular dyssynchrony cutoff value of 25.5° for intraventricular synchrony yielded 91.4% sensitivity and 84.4% specificity for predicting a good response to CRT.

CONCLUSIONS

The quantification of interventricular dyssynchrony with radionuclide phase analysis suggests that early postimplantation interventricular dyssynchrony may provide identification of CRT responders.

Interventricular delay measurement using equilibrium radionuclide angiography before resynchronization therapy should be performed outside the area of segmental wall motion abnormalities

BACKGROUND

The aim of this study was to demonstrate that only mechanical dyssynchrony outside the area of segmental wall motion abnormalities (WMA) can be reduced by cardiac resynchronization therapy (CRT).

METHODS AND RESULTS

Included in the study were 28 consecutive patients with nonischaemic cardiomyopathy selected for CRT. Equilibrium radionuclide angiography (ERNA) was carried out before and after implantation of a multisite pacemaker. Patients were separated into two groups depending on the presence or absence of segmental WMA.

RESULTS

A reduction in QRS duration was observed in all patients after CRT. The interventricular delay (IVD) decreased significantly after CRT only in patients without WMA (homogeneous contraction, HG group; IVD 44 ± 11.4° vs. 17 ± 3.1°, p = 0.04). In contrast, no significant decrease was observed in patients with WMA (WMA group; IVD 51 ± 6° vs. 38 ± 6°, p NS). However, when dyssynchrony was considered outside the WMA area, a significant reduction in IVD was obtained, in the same range as in the HG group (IVD 32 ± 3° vs. 19 ± 3°, p = 0.04). In 9 of 15 patients (60%) with a reduction in IVD after CRT, the left ventricle ejection fraction (LVEF) increased by about +10%. In contrast, in 13 of 13 patients (100%) with no reduction in IVD, no modification of LVEF was obtained. In the presence of segmental WMA without significant delays outside the WMA area, no reduction in IVD was observed and LVEF did not increase (IVD 34 ± 5° before CRT vs. 37 ± 7° after CRT; LVEF 19 ± 4% before CRT vs. 22 ± 3% after CRT, p NS).

CONCLUSION

ERNA can be used to predict good mechanical resychronization (decrease in IVD) in patients after pacing. IVD has to be determined excluding the area of WMA in order to select patients who will show an increase in their left ventricle function after CRT.

Ventricular-arterial and ventricular-ventricular interactions and their relevance to diastolic filling

Chronic heart failure is a common clinical problem, and, until recently, attention has focused predominantly on those patients with reduced left ventricular (LV) systolic function, as evidenced by a reduced LV ejection fraction. However, nearly half of all patients thought clinically to have heart failure have a "preserved" LV ejection fraction, variously defined as greater than 40% to 45% ("heart failure with normal ejection fraction" syndrome). The interaction of the heart with the systemic vasculature, termed ventricular-arterial coupling, is a key determinant of cardiovascular performance. The capacity of the body to augment cardiac output, regulate systemic blood pressure, and respond appropriately to elevations in heart rate and preload depends on both the properties of the heart and the properties of the vasculature into which the heart ejects blood. Although the marked increase of arterial and cardiac stiffness with aging can maintain ventricular-vascular coupling within a normal range, it does have detrimental effects on hemodynamic stability and cardiac reserve. Patients with heart failure with normal ejection fraction have been shown to have both arterial and ventricular stiffening, resulting in enhanced pressure-load dependence and sensitivity of blood pressure to circulating volume and diuretics. There is also indirect evidence to suggest that on exercise, increased external constraint to LV filling (as a result of diastolic ventricular interaction and pericardial constraint) may contribute to impaired use of the Starling mechanism in this group of patients.

Diastolic ventricular interaction: from physiology to clinical practice

The ventricles share a common septum and, therefore, the filling of one influences the compliance of the other. This phenomenon is known as direct diastolic ventricular interaction. The interaction is noticeably increased when the force exerted by the surrounding pericardium is raised, which is termed pericardial constraint. In healthy individuals, pericardial constraint is minor in the resting state. When right ventricular volume-to-pressure ratio acutely increases, however, such as during exercise, massive pulmonary embolism, or right ventricular infarction, notable diastolic ventricular interaction occurs. In this setting, the measured left ventricular intracavitary diastolic pressure overestimates the true left ventricular filling pressure, because the effect of external forces must be subtracted. Although growth of the pericardium can be a feature of chronic cardiac enlargement, here we review the evidence of the importance of diastolic ventricular interaction in certain acute and chronic disease processes, including heart failure.

Echocardiography-based optimization of cardiac resynchronization therapy in patients with congestive heart failure and conduction disorders

Resynchronization of segmental left ventricular mechanics as well as re-coordination of both atrio-ventricular and inter-ventricular contraction are potential mechanisms responsible for the clinical benefit observed in patients with advanced congestive heart failure treated by cardiac resynchronization therapy (CRT). Initially electrical conduction problems, in the majority of cases a left bundle branch block (LBBB), were considered the target for CRT. However, growing experience with CRT in different patient populations including those with milder degrees of conduction disturbance, and improved cardiac imaging utilizing the tissue Doppler approach, have shown the complexity of CRT and the usefulness of sophisticated echocardiographic imaging techniques for therapeutic decision making and optimization of CRT device settings.

A unique method by which to quantitate synchrony with equilibrium radionuclide angiography

BACKGROUND

Cardiac resynchronization therapy (CRT) improves symptoms and the survival rate in patients with advanced heart failure by improving synchrony. However, CRT is not always successful, is costly, and is applied without individualization. There is no specific measure of synchrony. The goal of this study was to analyze new quantitative parameters of synchrony and compare them with established measures.

METHODS AND RESULTS

Equilibrium radionuclide angiography, phase angle (Ø), and amplitude quantitate regional contraction timing and magnitude and are the basis for new synchrony (S) and entropy (E) parameters. S is the vector sum of all amplitudes based on the angular distribution of Ø divided by the scalar sum of the length of all vectors. Complete S equals 1, and its absence equals 0. E measures the disorder in the region of interest, is 1 with random contraction and 0 with full synchrony, and differentiates among differing contraction patterns. Left ventricular S and E were measured in 22 normal equilibrium radionuclide angiography studies, where regions of interest were drawn from the left ventricle, left atrium, and background to analyze model ventricles with normal wall motion (N), ventricles with aneurysm (An), ventricles with severe diffuse dysfunction (Diff), and ventricles with severe regional dysfunction (Reg). The new S and E parameters were highly reproducible and well differentiated among N, An, Diff, and Reg, which were not separated by SD Ø (SD of ventricular phase), which has gained popularity as a measure of synchrony.

CONCLUSION

Unique scintigraphic parameters for the evaluation of ventricular synchrony were derived, and their added value was determine compared with established measures. Indications for pacemaker therapy now include the treatment of severe congestive heart failure (CHF). Atrial triggered biventricular pacemakers reduce CHF symptoms and prolong life in patients with cardiomyopathy, severe CHF, left ventricular (LV) ejection fraction (EF) lower than 35%, and QRS greater than 120 milliseconds. Such pacing, or cardiac resynchronization therapy (CRT), seeks to reduce the heterogeneity and increase the synchrony of ventricular activation, conduction, and contraction. CRT has improved hemodynamics, increased exercise tolerance, reduced symptoms and the need for hospitalization, reversed ventricular remodeling, and reduced the all-cause mortality rate in CHF. However, CRT is costly, fails to improve symptoms or activity level in more than 30% of patients, and is applied blindly without individualization or consideration of lead placement sight. A variety of echocardiographic methods have sought to measure synchrony and its serial changes with CRT. A recent study presented evidence of the poor reproducibility of several widely applied echocardiographic measurements by which to determine ventricular synchrony. Magnetic resonance imaging has excellent resolution of regional wall motion and has been applied to assess ventricular synchrony and its response to pacing therapy. However, these methods are complex and are not well established or widely available, and magnetic resonance imaging has not been widely applied after pacing. An accurate and reproducible method is needed by which to objectively measure regional ventricular synchrony. Phase image analysis, a functional method based on the first Fourier harmonic fit of the gated blood pool time versus radioactivity curve, generates the parameters of amplitude (A), which parallels the extent of regional ventricular contraction or stroke volume, and phase angle (Ø), which represents the timing of regional contraction. It was applied early with demonstrated reproducibility to show the linkage between electrical and mechanical dyssynchrony and to characterize the contraction pattern in heart failure and its alteration with CRT. The SD of ventricular Ø, applied as a marker of synchrony, has been shown to demonstrate the beneficial effects of biventricular pacing, and its strong prognostic value has been shown in patients with congestive cardiomyopathy and CHF, superior to LVEF. The SD Ø may not be optimal for synchrony evaluation. We sought improved, more sensitive parameters to better differentiate synchrony among the spectrum of possible patterns of dyssynergy. We derived, initially evaluated, and here present new synchrony (S) and entropy (E) parameters, based on the phase method, to quantitate regional and global ventricular synchrony and applied them in simulation and clinical protocols.

Left Ventricular Pacing Minimizes Diastolic Ventricular Interaction, Allowing Improved Preload-Dependent Systolic Performance

Background— Left ventricular (LV) pacing improves hemodynamics in patients with heart failure. We hypothesized that at least part of this benefit occurs by minimization of external constraint to LV filling from ventricular interaction.

Methods and Results— We present median values (interquartile ranges) for 13 heart failure patients with LV pacing systems implanted for New York Heart Association class III/IV limitation. We used the conductance catheter method to measure LV pressure and volume simultaneously. External constraint was measured from the end-diastolic pressure-volume relation recorded during inferior vena caval occlusion, during LV pacing, and while pacing was suspended. External constraint to LV filling was reduced by 3.0 (4.6 to 0.6) mm Hg from 4.8 (0.6 to 7.5) mm Hg ( P <0.01) in response to LV pacing; effective filling pressure (LV end-diastolic pressure minus external constraint) increased by 4.0 (2.2 to 5.8) mm Hg from 17.7 (13.3 to 22.6; P <0.01). LV end-diastolic volume increased by 10 (3 to 11) mL from 238 (169 to 295) mL ( P =0.01), whereas LV end-systolic volume did not change significantly (−1 [−2 to 3] mL from 180 [124 to 236] mL, P =0.97), which resulted in an increase in stroke volume of 11 (5 to 13) mL from 49 (38 to 59) mL ( P <0.01). LV stroke work increased by 720 (550 to 1180) mL · mm Hg from 3400 (2110 to 4480) mL · mm Hg ( P =0.01), and maximum dP/dt increased by 120 (2 to 161) mm Hg/s from 635 (521 to 767) mm Hg/s ( P =0.03).

Conclusions— This study suggests a potentially important mechanism by which LV pacing may produce hemodynamic benefit. LV pacing minimizes external constraint to LV filling, resulting in an increase in effective filling pressure; the consequent increase in LV end-diastolic volume increases stroke volume via the Starling mechanism.

Gated blood pool SPECT improves reproducibility of right and left ventricular Fourier phase analysis in radionuclide angiography

OBJECTIVES

The ventricular phase angle, a parametric method applied to Fourier phase analysis (FPA) in radionuclide ventriculography, allows the quantitative analysis of ventricular contractile synchrony. However, FPA reproducibility using gated blood pool SPECT (GBPS) has not been fully evaluated. The present study evaluates whether by using GBPS, the reproducibility of FPA could be improved over that in planar radionuclide angiography (PRNA).

METHODS

Forty-three subjects underwent both GBPS and PRNA, of which 10 subjects were normal controls, 25 had dilated cardiomyopathy, and 8 had various heart diseases. Interventricular contractile synchrony was measured as the absolute difference in RV and LV mean ventricular phase angle as delta(phi) (RV - LV). Intraventricular contractile synchrony was measured as the standard deviation of the mean phase angle for the RV and LV blood pools (RVSD(phi), LVSD(phi)). Two nuclear physicians processed the same phase images of GBPS to evaluate the interobserver reproducibility of the phase angles using data from the 43 study participants. Phase images acquired from PRNA were processed in the same manner.

RESULTS

Excellent reproducibility of delta(phi) (RV - LV) was obtained with both GBPS (Y = -3.10 + 0.89 x X; r = 0.901) and PRNA (Y = -4.51 + 0.81 x X; r = 0.834). In regard to RVSD(phi) reproducibility was not adequate with PRNA (Y = 18.56 + 0.35 x X; r = 0.424), while it was acceptable with GBPS (Y = 5.22 + 0.85 x X; r = 0.864). LVSD(phi) reproducibility was superior using both GBPS (Y = 4.15 + 0.97 x X; r = 0.965) and PRNA (Y = -0.55 + 0.98 x X; r = 0.910).

CONCLUSION

Our results demonstrate FPA obtained using GBPS to be highly reproducible for evaluating delta(phi) (RV - LV), RVSD(phi) and LVSD(phi), in comparison with the PRNA method. We thus consider GBPS appropriate for evaluating ventricular contractile synchrony.

Midterm Benefits of Left Univentricular Pacing in Patients With Congestive Heart Failure

Background— Resynchronization therapy by simultaneous pacing of the right and left ventricles has gained wide acceptance as a useful treatment for patients with severe congestive heart failure. Several short-term hemodynamic studies in humans and animals failed to demonstrate any benefit of biventricular pacing over left univentricular pacing, but long-term studies on this pacing mode are lacking. The objective of this study was to assess the outcome over a 1-year period of patients paced exclusively in the left ventricle.

Methods and Results— Clinical, angiographic, echocardiographic, and ergometric data were collected at baseline and after 12 months in 22 patients (age, 69.3±6.5 years) with NYHA class III or IV (10 patients), sinus rhythm, left bundle-branch block, and no bradycardia indication for pacing. After 12 months, compared with baseline values, NYHA class improved significantly by 40% ( P <0.0001), 6-minute walk distance by 30% ( P =0.01), peak V̇ o 2 by 26% ( P =0.01), left ventricular end-diastolic diameter by 5% ( P =0.02), ejection fraction by 22% ( P =0.07), mitral regurgitation area by 40% ( P =0.01), and norepinephrine level by 37% ( P =0.04).

Conclusions— In patients with severe congestive heart failure, sinus rhythm, and left bundle-branch block despite optimal pharmacological treatment, left univentricular pacing is feasible and results in significant midterm benefit in exercise tolerance and left ventricular function.

Current status of cardiac resynchronization therapy

PURPOSE OF REVIEW

Cardiac resynchronization therapy with biventricular pacing has rapidly emerged as an indispensable treatment option in patients with moderate-to-advanced heart failure and left bundle branch block. New findings on the pathophysiology of cardiac resynchronization therapy and its clinical effects are reviewed.

RECENT FINDINGS

Several randomized trials have evaluated the effects of cardiac resynchronization therapy on cardiac haemodynamics and clinical parameters in selected heart failure patients with left bundle branch block. The effects of cardiac resynchronization therapy on mechanical synchrony have been evaluated by different imaging modalities, such as echocardiography and radionuclide angiography. Cardiac resynchronization therapy leads to improved haemodynamics at a diminished energy cost, and improves functional mitral regurgitation. This haemodynamic improvement is associated with a significantly better quality of life, improved exercise capacity, and less frequent hospitalization. Recent preliminary data suggest a positive effect on cardiac mortality. However, approximately a third of implanted patients do not benefit from cardiac resynchronization therapy, and therefore additional criteria for the identification of mechanical dyssynchrony are needed to identify those patients who will respond before implantation.

SUMMARY

Many randomized trials have confirmed the benefits of cardiac resynchronization therapy in selected heart failure patients. The successful resynchronization of the ventricular activation-contraction sequence is the major determinant of acute haemodynamic and long-term clinical improvement. The diagnostic sensitivity and specificity of the non-invasive identification of mechanical dyssynchrony may be improved by echocardiography, but further research is needed to identify the optimal strategy for patient identification.

Basal asynchrony and resynchronization with biventricular pacing predict long-term improvement of LV function in heart failure patients

Biventricular pacing (BiV) is emerging for patients with dilated cardiomyopathy (DCM) and asynchrony. We measured basal asynchrony and early resynchronization by radionuclide angioscintigraphy (RNA) in order to predict long-term evolution of ventricular function after BiV. Thirty-four patients (NYHA Class III-IV,65.4 +/- 11 years) with large QRS(179 +/- 18 ms)were implanted with BiV and studied by RNA before (D0), at day 8 (D8), and during follow-up(20 +/- 7 months). We calculated left and right ejection fractions, the interventricular dyssynchrony (TRVLV), and the apicobasal dyssynchrony (Tab). LVEF improved from 20.2 +/- 8.1%(D0) to27.1%+/- 12.6%(follow-up,P < 0.003 vs D0) and RVEF from 28.6%+/- 13%(D0) to 34.3 +/- 11.5%(follow-up,P < 0.03 vs D0). Inter- (DeltaTRVLV) and intraventricular resynchronization was immediate and remained stable: TRVLV decreased from 68.3 +/- 38 ms(D0) to 13.4 +/- 48.5 ms(D8) and1.8 +/- 39.2 ms(follow-up,P < 0.0001 vs D0); and Tab from 45.8 +/- 64.1 msto-18 +/- 68(D8) and-28.3 +/- 53.6 ms(follow-up,P < 0.0001 vs D0). Early inter- and intraventricular resynchronization (DeltaTab) at D8 were related to late LVEF and RVEF improvement. Together, an LVEF > 15% and a significant interventricular dyssynchrony (TRVLV > 60 ms) at D0 have a sensitivity of 79% and a positive predictive value of 83% to predict an improvement of LVEF superior to 5% at follow-up. In DCM patients, BiV resynchronizes ventricles early and in the long-term, while RVEF and LVEF improve progressively. Patients with large electromechanical dyssynchrony benefit most from BiV.

Interventricular and intraventricular dyssynchrony in idiopathic dilated cardiomyopathy: a prognostic study with fourier phase analysis of radionuclide angioscintigraphy

OBJECTIVES

The study evaluated the prognostic value of interventricular and intraventricular dyssynchrony in idiopathic dilated cardiomyopathy (IDC).

BACKGROUND

Biventricular pacing is an emerging treatment for patients with dilated cardiomyopathy and ventricular dyssynchrony. The prognostic values of interventricular and intraventricular dyssynchrony have not been previously compared.

METHODS

A total of 103 patients with IDC were studied. Left bundle branch block was present in 25% of patients. Equilibrium radionuclide angiography was performed and Fourier phase analyses were examined in both ventricles. Difference between the mean phase of left ventricle (LV) and right ventricle (RV) assessed interventricular dyssynchrony, and standard deviations (SDs) of the mean phase in each ventricle assessed intraventricular dyssynchrony.

RESULTS

The QRS duration was related to both interventricular and intraventricular dyssynchrony. A degradation of the hemodynamic status was associated with an increase in intraventricular dyssynchrony but not in interventricular dyssynchrony. With a follow-up of 27 +/- 23 months, 18 patients had a major cardiac event (7 cardiac deaths; 11 worsening, leading to heart transplantation). The SDs of the LV and RV mean phase and QRS duration were predictors of cardiac event (all p < 0.0001), but interventricular dyssynchrony was not. Among 13 univariate predictors of cardiac event, the only independent predictors were an increased SD of LV mean phase (p = 0.0004) and an increased pulmonary capillary wedge pressure (p = 0.009).

CONCLUSIONS

Intraventricular dyssynchrony evaluated with phase analysis of radionuclide angiography is an independent predictor of cardiac event in IDC. The prognosis is related to intraventricular rather than to interventricular dyssynchrony in IDC.

Cine-MR Fourier phase imaging for quantification of regional wall asynergy in patients with anterior myocardial infarction

PURPOSE

The aim of this study was to evaluate whether Fourier analysis of cine-MR could detect wall motion abnormalities in patients with myocardial infarction.

METHODS

Ten patients with anterior myocardial infarction (seven men and three women; mean age, 58 +/- 16 years) were compared with six control subjects (four men and two women; mean age, 49 +/- 24 years). Gradient echo cardiac cine-MR slices were transformed using a commercially available Fourier algorithm to obtain phase angles of endocardial segments. Mean phase angle and phase dispersion (i.e., SD around the mean) were calculated. Segmental wall motion was evaluated using a 16-segment model and correlated to Fourier phase analysis.

RESULTS

Mean phase angle and phase dispersion were increased in patients compared with control subjects (respectively, 191 degrees +/- 23 degrees vs. 161 degrees +/- 25 degrees, P < 0.0001 and 21 degrees +/- 10 degrees vs. 11 degrees +/- 8 degrees, P = 0.0007). Analysis of variance showed a significant increased dispersion on basal slices (P = 0.002) mostly due to flow-void and entry slice phenomenon.

CONCLUSIONS

Fourier phase analysis of cardiac cine-MR is feasible and allows the evaluation of ventricular asynergy on the basis of endocardial wall motion.

Tissue Doppler imaging predicts improved systolic performance and reversed left ventricular remodeling during long-term cardiac resynchronization therapy

OBJECTIVES

We sought to evaluate the long-term impact of cardiac resynchronization therapy (CRT) on left ventricular (LV) performance and remodeling using three-dimensional echocardiography and tissue Doppler imaging (TDI).

BACKGROUND

Three-dimensional echocardiography and TDI allow rapid and accurate evaluation of LV volumes and performance.

METHODS

Twenty-five consecutive patients with severe heart failure and bundle branch block who underwent biventricular pacemaker implantation were included. Before and after implantation of the pacemaker, three-dimensional echocardiography and TDI were performed. These examinations were repeated at outpatient visits every six months.

RESULTS

Five patients (20%) died during one-year follow-up. In the remaining 20 patients, significant reductions in LV end-diastolic volume and LV end-systolic volume of 9.6 +/- 14% and 16.5 +/- 15%, respectively (p < 0.01), could be demonstrated during long-term follow-up. Accordingly, LV ejection fraction increased by 21.7 +/- 18% (p < 0.01). According to a newly developed TDI technique-tissue tracking-all regional myocardial segments improved their longitudinal systolic shortening (p < 0.01). The extent of the LV base displaying delayed longitudinal contraction, as detected by TDI before pacemaker implantation, predicted long-term efficacy of CRT. The QRS duration failed to predict resynchronization efficacy.

CONCLUSIONS

Cardiac resynchronization significantly improved LV function and reversed LV remodeling during long-term follow-up. Patients likely to benefit from CRT can be identified by TDI before implantation of a biventricular pacemaker.

Echocardiographic quantification of left ventricular asynchrony predicts an acute hemodynamic benefit of cardiac resynchronization therapy

OBJECTIVES

We sought to determine whether radial left ventricular (LV) asynchrony in patients with heart failure predicts systolic function improvement with cardiac resynchronization therapy (CRT).

BACKGROUND

We quantified LV wall motion by echocardiography to correlate the effects of CRT on LV systolic function with wall motion synchrony.

METHODS

Thirty-four patients underwent echocardiographic phase analysis of LV septal and lateral wall motion and hemodynamic testing before CRT. Phase relationships were measured by the difference between the lateral (Phi(L)) and septal (Phi(S)) wall motion phase angles: Phi(LS) = Phi(L) - Phi(S). The absolute value of Phi(LS) was used as an order-independent measure of synchrony: the absolute value Phi(LS) = the absolute value of Phi(L) - Phi(S).

RESULTS

Three phase relationships were identified (mean +/- SD): type 1 (n = 4; peak positive LV pressure [dP/dt(max)] 692 +/- 310 mm Hg/s; Phi(LS) = 5 +/- 6 degrees, synchronous wall motion); type 2 (n = 17; dP/dt(max) 532 +/- 148 mm Hg/s; Phi(LS) = 77 +/- 33 degrees, delayed lateral wall motion); and type 3 (n = 13; dP/dt(max) 558 +/- 154 mm Hg/s; Phi(LS) = -115 +/- 33 degrees, delayed septal wall motion, triphasic). A large absolute value of Phi(LS) predicted a larger increase in dP/dt(max) with CRT (r = 0.74, p < 0.001). Sixteen patients were studied during right ventricular (RV), LV and biventricular (BV) pacing. Cardiac resynchronization therapy acutely reduced the absolute value of Phi(LS) from 104 +/- 41 degrees (OFF) to 86 +/- 45 degrees (RV; p = 0.14 vs. OFF), 71 +/- 50 degrees (LV; p = 0.001 vs. OFF) and 66 +/- 42 degrees (BV; p = 0.001 vs. OFF). A reduction in the absolute value of Phi(LS) predicted an improvement in dP/dt(max) in type 2 patients for LV (r = 0.87, p = 0.005) and BV CRT (r = 0.73, p = 0.04).

CONCLUSIONS

Echocardiographic quantification of LV asynchrony identifies patients likely to have improved systolic function with CRT. Improved synchrony is directly related to improved hemodynamic systolic function in type 2 patients.

Acute effects of cardiac resynchronization therapy on left ventricular Doppler indices in patients with congestive heart failure

BACKGROUND

Patients with heart failure frequently exhibit intraventricular conduction delays, which contribute to asynchronous contraction patterns and impaired hemodynamic performance. Cardiac resynchronization therapy (CRT) with biventricular (BV) and left ventricular (LV) pacing has been shown to improve both hemodynamic and clinical performance. This study investigated the effects of CRT on LV Doppler indices in these patients.

METHODS AND RESULTS

Thirty-two patients with advanced heart failure (New York Heart Association class > or =III, QRS >120 milliseconds, PR interval >150 milliseconds) were studied 4 weeks after implantation of a CRT system. Doppler echocardiography was conducted in 3 separate CRT modes, right ventricular, LV, and BV stimulation at 3 different atrioventricular delays. CRT resulted in significant improvement of Doppler parameters such as filling time (FT, 313 +/- 111 milliseconds at baseline --> 363 +/- 154 milliseconds [BV], P <.05), aortic velocity time integral (AO(VTI) 23.2 +/- 7.4 cm at baseline --> 26.8 +/- 8.8 cm [LV], P <.05), and the myocardial performance index (MPI, 1.21 +/- 0.51 at baseline --> 0.85 +/- 0.34 [BV], P <.05). The most improvement was observed with LV and BV stimulation at short and intermediate atrioventricular delays (80-120 milliseconds), independent of ischemic or idiopathic origin.

CONCLUSIONS

CRT improves hemodynamic performance in patients with heart failure with intraventricular conduction delays. Doppler echocardiography allows noninvasive evaluation of acute CRT effects in patients with heart failure. In particular, FT, AO(VTI), and MPI are useful parameters for noninvasive follow-up and optimization of pacing parameters.

Left ventricular and biventricular pacing in congestive heart failure

Dual-chamber pacing improved hemodynamics acutely in a subset of patients with left ventricular (LV) dysfunction but conveyed no long-term symptomatic benefit in most. More recently, LV pacing and biventricular (multisite) pacing have been used to improve systolic contractility by altering the electrical and mechanical ventricular activation sequence in patients with severe congestive heart failure (CHF) and intraventricular conduction delay or left bundle branch block (LBBB). Intraventricular conduction delay and LBBB cause dyssynchronous right ventricular and LV contraction and worsen LV dysfunction in cardiomyopathies. Both LV and biventricular cardiac pacing are thought to improve cardiac function in this situation by effecting a more coordinated and efficient ventricular contraction. Short-term hemodynamic studies have shown improvement in LV systolic function, which seems more pronounced with monoventricular LV pacing than with biventricular pacing. Recent clinical studies in limited numbers of patients suggest long-term clinical benefit of biventricular pacing in patients with severe CHF symptoms. Continuing and future studies will demonstrate whether and in which patients LV and biventricular pacing are permanently effective and equivalent and which pacing site within the LV produces the most beneficial hemodynamic results.