Left ventricular dyssynchrony predicts response and prognosis after cardiac resynchronization therapy

Tissue Doppler Imaging and Left Ventricular Dyssynchrony in Heart Failure

BACKGROUND

Electrical dyssynchrony is one of the main criteria for determining eligibility for cardiac resynchronization therapy (CRT). However, recent data support the use of mechanical rather than electrical dyssynchrony as the major criterion for receiving CRT.

METHODS AND RESULTS

Tissue Doppler imaging (TDI) is emerging as an indispensable tool for measuring and quantifying mechanical dyssynchrony in patients with advanced heart failure. TDI techniques for quantifying dyssynchrony include: tissue tracking, tissue velocity imaging, tissue synchronization imaging, and strain analysis. This review details the different techniques and discusses advantages and disadvantages of each. As TDI is incorporated into clinical practice, the ability to select patients who are most likely to improve after CRT should increase. TDI may also prove to be a useful tool for optimizing pacemaker settings in patients who do not improve after CRT.

CONCLUSION

Ongoing research trials will further define the role of TDI in the clinical management of patients with heart failure.

Effect of Posterolateral Scar Tissue on Clinical and Echocardiographic Improvement After Cardiac Resynchronization Therapy

Background— Currently, one third of patients treated with cardiac resynchronization therapy (CRT) do not respond. Nonresponse to CRT may be explained by the presence of scar tissue in the posterolateral left ventricular (LV) segments, which may result in ineffective LV pacing and inadequate LV resynchronization. In the present study, the relationship between transmural posterolateral scar tissue and response to CRT was evaluated.

Methods and Results— Forty consecutive patients with end-stage heart failure (NYHA class III/IV), LV ejection fraction ≤35%, QRS duration >120 ms, left bundle-branch block, and chronic coronary artery disease were included. The localization and transmurality of scar tissue were evaluated with contrast-enhanced MRI. Next, LV dyssynchrony was assessed at baseline and immediately after implantation with tissue Doppler imaging. Clinical parameters, LV volumes, and LV ejection fraction were assessed at baseline and at a 6-month follow-up. Fourteen patients (35%) had a transmural (>50% of LV wall thickness) posterolateral scar. In contrast to patients without posterolateral scar tissue, these patients showed a low response rate (14% versus 81%; P <0.05) and did not show improvement in clinical or echocardiographic parameters. In addition, LV dyssynchrony remained unchanged after CRT implantation (84±46 versus 78±41 ms; P =NS). Patients without posterolateral scar tissue and severe baseline dyssynchrony (≥65 ms) showed an excellent response rate of 95% compared with patients with a posterolateral scar and/or absent LV dyssynchrony (11%).

Conclusions— CRT does not reduce LV dyssynchrony in patients with transmural scar tissue in the posterolateral LV segments, resulting in clinical and echocardiographic nonresponse to CRT.

Novel speckle-tracking radial strain from routine black-and-white echocardiographic images to quantify dyssynchrony and predict response to cardiac resynchronization therapy

BACKGROUND

Mechanical dyssynchrony is a potential means to predict response to cardiac resynchronization therapy (CRT). We hypothesized that novel echocardiographic image speckle tracking can quantify dyssynchrony and predict response to CRT.

METHODS AND RESULTS

Seventy-four subjects were studied: 64 heart failure patients undergoing CRT (aged 64+/-12 years, ejection fraction 26+/-6%, QRS duration 157+/-28 ms) and 10 normal controls. Speckle tracking applied to routine midventricular short-axis images calculated radial strain from multiple circumferential points averaged to 6 standard segments. Dyssynchrony from timing of speckle-tracking peak radial strain was correlated with tissue Doppler measures in 47 subjects (r=0.94, P<0.001; 95% CI 0.90 to 0.96). The ability of baseline speckle-tracking radial dyssynchrony (time difference in peak septal wall-to-posterior wall strain > or =130 ms) to predict response to CRT was then tested. It predicted an immediate increase in stroke volume in 48 patients studied the day after CRT with 91% sensitivity and 75% specificity. In 50 patients with long-term follow-up 8+/-5 months after CRT, baseline speckle-tracking radial dyssynchrony predicted a significant increase in ejection fraction with 89% sensitivity and 83% specificity. Patients in whom left ventricular lead position was concordant with the site of latest mechanical activation by speckle-tracking radial strain had an increase in ejection fraction from baseline to a greater degree (10+/-5%) than patients with discordant lead position (6+/-5%; P<0.05).

CONCLUSIONS

Speckle-tracking radial strain can quantify dyssynchrony and predict immediate and long-term response to CRT and has potential for clinical application.

Implantable devices for management of chronic heart failure: defibrillators and biventricular pacing therapy

PURPOSE OF REVIEW

With chronic heart failure already an epidemic in the USA, its prevalence is expected to rise significantly in the future. Despite improved survival with pharmacologic therapy, the morbidity and mortality of patients with heart failure remain high. The purpose of this review, therefore, is to present recent data on the non-pharmacologic, device-based treatment of patients with chronic heart failure.

RECENT FINDINGS

The implantable cardioverter-defibrillator has become standard treatment for the prevention of sudden, arrhythmic death. Recent well-designed clinical trials have led to device-based therapy as an important component in the management of patients with systolic left ventricular dysfunction (resulting from both ischemic and non-ischemic etiologies) and symptomatic chronic heart failure. Implantable cardioverter-defibrillator therapy alone (without biventricular pacing) results in a significant reduction in the overall mortality of patients with mild and moderate heart failure. Biventricular pacing (or cardiac resynchronization therapy) with or without a back-up implantable cardioverter-defibrillator, compared with optimal pharmacologic therapy, improves symptoms, quality of life, exercise tolerance, left ventricular function, and the survival of patients with advanced heart failure, a left ventricular ejection fraction of 35% or less, and intraventricular conduction delays (QRS > 120 ms), although up to approximately 30% of patients do not respond to cardiac resynchronization therapy. Ongoing and planned studies should clarify which patients are most likely to respond to cardiac resynchronization therapy and elucidate its role in those with a normal (< 120 ms) QRS (approximately 70% of patients with heart failure).

SUMMARY

Device therapy (implantable cardioverter-defibrillator and cardiac resynchronization therapy) should be considered an integral, but adjunctive, part of the management of patients with chronic heart failure who are receiving appropriate medical therapy. The type of device used will depend on the individual patient's clinical characteristics.

Optimization of Pulsed Wave Tissue Doppler to Predict Left Ventricular Reverse Remodeling After Cardiac Resynchronization Therapy

OBJECTIVE

The optimal use of pulsed wave Doppler tissue imaging (DTI) in predicting left ventricular (LV) reverse remodeling after cardiac resynchronization therapy (CRT) was investigated.

METHODS

DTI was performed in 69 patients before and 3 months after CRT. Echocardiographic reverse remodeling was observed in 38 patients. LV dyssynchrony was measured with the time to onset or peak systolic velocity in 2- and 6-basal segment models.

RESULTS

The time to onset and either the standard deviation of 6 segments of > 20 ms or a delay of > or = 60 ms between any 2 of 6 segments had a similar predictive accuracy (sensitivity, 97% and 95%, respectively; specificity, 74% and 73%, respectively). The time to peak systolic velocity or evaluating 2 segments was less accurate.

CONCLUSIONS

Evaluation of 6 segments is necessary to predict LV reverse remodeling after CRT. The time to onset of systolic velocity is superior to the time to peak velocity.

Effects of cardiac resynchronization therapy on disease progression in chronic heart failure

Despite the alleviation of symptoms and longer survival conferred by pharmacological management of chronic congestive heart failure (CHF), this progressive syndrome remains associated with high morbidity and premature death. A new treatment of CHF should ideally alleviate symptoms, improve functional capacity, decrease mortality, and slow or reverse its progression without adding risks for the patient that outweighs the benefits. Growing evidence indicates that devices implanted to resynchronize ventricular contraction are a beneficial adjunct in the treatment of CHF. This review discusses the remodelling process, and its clinical and prognostic significance. We also discuss the impact of CRT, on remodelling and disease progression with a particular focus on patients with asymptomatic or mild heart failure (NYHA Class I-II).

Clinical versus echocardiographic parameters to assess response to cardiac resynchronization therapy

Currently, a clear definition of response to cardiac resynchronization therapy (CRT) is still lacking, and clinical and echocardiographic end points are used. It is also unclear whether patients with clinical responses also improve in echocardiographic end points (and vice versa). To better understand and define response to CRT, the relation between improvement in clinical and echocardiographic parameters was evaluated in 144 patients.

Temas de actualidad en estimulación cardíaca 2005

Currently, three areas of active development in cardiac pacing are of particular interest to clinical cardiologists. Biventricular pacing is now considered a type-I indication for adjuvant treatment in advanced and refractory heart failure. Consequently, some changes in everyday clinical practice will be seen when patients with end-stage heart failure start to receive resynchronization therapy. Secondly, the Cardiac Pacing Working Group of the Spanish Society of Cardiology has developed a national consensus document on sleep apnea and cardiac rhythm abnormalities. It appears that a novel way of tackling the current growing epidemic could be to use permanent cardiac pacing in an attempt to modify the cardiac rhythm alterations, mainly bradyarrhythmias, related to sleep apnea. Finally, promising developments are taking place in systems designed to reduce the unwanted right ventricular stimulation sometimes observed with antibradycardia pacing modalities. These new systems are expected to minimize significantly the well-known deleterious hemodynamic effects sometimes seen in our patients.

Comparison of myocardial velocities obtained with magnetic resonance phase velocity mapping and tissue doppler imaging in normal subjects and patients with left ventricular dyssynchrony

PURPOSE

To compare longitudinal myocardial velocity and time to peak longitudinal velocity obtained with magnetic resonance phase velocity mapping (MR-PVM) and tissue Doppler imaging (TDI), and to assess the reproducibility of each method.

MATERIALS AND METHODS

Longitudinal myocardial velocity was measured by TDI and MR-PVM in 10 normal volunteers and 10 patients with dyssynchrony. The reproducibility of MR-PVM and TDI was assessed on repeated measurements in the 10 normal volunteers.

RESULTS

MR and TDI measurements of longitudinal myocardial velocity correlated well (r = 0.86) in both normal subjects and patients with dyssynchrony. However, myocardial velocities measured with MR consistently exceeded velocities measured with TDI. MR and TDI agreed strongly in measuring the time to peak velocity (r = 0.97). The reproducibility of TDI and MR-PVM appeared similar in measuring peak velocities (13.1% vs. 11.0%, respectively; P = NS) and time to peak velocity (9.1% vs. 5.7%, respectively; P = NS).

CONCLUSION

Excellent correlation and reproducibility were observed between MR-PVM and TDI in measuring longitudinal myocardial velocity and time to peak velocity in both normal subjects and patients with dyssynchrony.

The problem of non-response to cardiac resynchronization therapy

PURPOSE OF REVIEW

Cardiac resynchronization therapy improves quality of life, exercise performance, left ventricular ejection fraction, and reduces heart failure hospitalizations and mortality in patients with New York Heart Association class III or IV congestive heart failure and intraventricular conduction delay. A number of key clinical research questions remain, perhaps most importantly the issue of why apparently suitable patients do not respond to cardiac resynchronization therapy. These issues are also relevant to patients who do respond to cardiac resynchronization therapy as potentially their response might be further increased. This article will review the data regarding the frequency of the problem of non-response to cardiac resynchronization therapy and then discuss the postulated reasons and potential solutions.

RECENT FINDINGS

Rates of non-response to cardiac resynchronization therapy are often quoted as 20-30%, but a critical analysis of the data would suggest the true non-responder rate can be estimated as perhaps 40-50%. The data indicate that on a population basis non-response is multi-factorial and the extent of mechanical dyssynchrony, left ventricular pacing site and cause of congestive heart failure are likely to be important. Ongoing research is exploring the utility of various techniques for quantifying mechanical dyssynchrony and the potential benefits of targeted left ventricular lead placement and post-implant optimization.

SUMMARY

Cardiac resynchronization therapy is a major breakthrough in treatment for advanced congestive heart failure patients. There is substantial rate of non-response to this therapy, however, and research is exploring various ways to increase the response to the technique.

Acceleration-Dependent Left Bundle Branch Block with Severe Left Ventricular Dyssynchrony Results in Acute Heart Failure: Are There More Patients Who Benefit from Cardiac Resynchronization Therapy?

Cardiac resynchronization therapy (CRT) has been proposed to improve hemodynamics in patients with heart failure and left bundle branch block (LBBB) by resynchronization of left ventricular (LV) dyssynchrony. The current report concerns a patient with narrow QRS complex without LV dyssynchrony who experienced an acute exacerbation of heart failure following exercise. Careful analysis revealed that an increase of heart rate induced acceleration-dependent LBBB with severe LV dyssynchrony and mitral regurgitation followed by acute heart failure and hemodynamic collapse. CRT prevented these adverse reactions. Accordingly, optimal evaluation for CRT may include testing for LV dyssynchrony during exercise.

Improvements in left ventricular diastolic function after cardiac resynchronization therapy are coupled to response in systolic performance

OBJECTIVES

To determine the short-term effects of cardiac resynchronization therapy (CRT) on measurements of left ventricular (LV) diastolic function in patients with severe heart failure.

BACKGROUND

Cardiac resynchronization therapy improves systolic performance; however, the effects on diastolic function by load-dependent pulsed-wave Doppler transmitral indices has been variable.

METHODS

Fifty patients with severe heart failure were evaluated by two-dimensional Doppler echocardiography immediately prior to and 4 +/- 1 month after CRT. Measurements included LV volumes and ejection fraction (EF), pulsed-wave Doppler (PWD)-derived transmitral filling indices (E- and A-wave velocities, E/A ratio, deceleration time [DT], diastolic filling time [DFT], and isovolumic relaxation time). Tissue Doppler imaging was used for measurements of systolic and diastolic (Em) velocities at four mitral annular sites; mitral E-wave/Em ratio was calculated to estimate LV filling pressure. Color M-mode flow propagation velocities were also obtained.

RESULTS

After CRT, LV volumes decreased significantly (p < 0.001) and LVEF increased >5% in 28 of 50 patients (56%) and were accompanied by reduction in PWD mitral E-wave velocity and E/A ratio (both p < 0.01), increased DT and DFT (both p < 0.01), and lower filling pressures (i.e., E-wave/Em septal; p < 0.01). Patients with LVEF response < or =5% after CRT had no significant changes in measurements of diastolic function; LV relaxation (i.e., Em velocities) worsened in this group.

CONCLUSIONS

In heart failure patients receiving CRT, improvement in LV diastolic function is coupled to the improvement in LV systolic function.

Cardiac resynchronization therapy and tools to identify responders

Heart failure is a major epidemic. Many people with heart failure struggle with refractory symptoms despite optimal medical therapy. Those with severe left ventricular dysfunction and ventricular conduction delay are at significant risk from either dying suddenly or dying from progression of their heart failure. Cardiac resynchronization therapy (CRT) improves hemodynamics and symptoms of heart failure and has recently been shown to improve survival. One problem facing the use of CRT is that 30% of patients fail to respond. The dominant theory is that QRS duration (electrical dyssynchrony) does not accurately reflect mechanical dyssynchrony. Echocardiographic tools have recently been developed that enable clinicians to assess the degree of mechanical dyssynchrony in patients being considered for CRT. These tools are able to predict with a significant amount of accuracy whether a patient will respond to CRT. This allows for a more refined approach to evaluating patients for CRT and optimizing the treatment of congestive heart failure.

Myocardial asynchronism is a determinant of changes in functional mitral regurgitation severity during dynamic exercise in patients with chronic heart failure due to severe left ventricular systolic dysfunction

AIMS

Functional mitral regurgitation (MR) and myocardial asynchronism occur commonly in patients with dilated cardiomyopathy and affect adversely their prognosis and symptoms. The aim of this study was to evaluate the mechanisms of changes in MR severity during dynamic exercise in patients with chronic heart failure (CHF).

METHODS AND RESULTS

Seventy patients with CHF due to left ventricular (LV) systolic dysfunction [LV ejection fraction (EF) <40%] and functional MR were studied. All were in sinus rhythm. Medications were left unchanged for the study. Each patient performed a maximal symptom-limited exercise test with continuous 2D-Doppler echocardiography. Mitral regurgitant volume (RV) and effective regurgitant orifice (ERO) were determined at rest and during exercise. LV asynchrony using Doppler tissue imaging and interventricular asynchrony using conventional pulsed-Doppler were evaluated at rest. Resting LV EF averaged 25+/-8%. Mean resting LV and interventricular mechanical delays were 56+/-50 and 43+/-37 ms, respectively. The overall median values for mitral ERO and RV did not significantly change during dynamic exercise (11 [7-16] vs. 11 [6-21] mm2 and 14 [10-22] vs. 12 [9-23] mL, respectively). However, changes in mitral ERO and RV were individually variable and significantly correlated with the degree of LV asynchronism (r=0.66, P<0.0001 and r=0.66, P<0.0001, respectively).

CONCLUSION

Changes in MR are variable during dynamic exercise. LV asynchronism at rest substantially contributes to worsening of functional MR during dynamic exercise in patients with CHF due to LV systolic dysfunction.

Cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) is a recently developed approach to treat dilated heart failure with discoordinate contraction. Such dyssynchrony typically stems from electrical delay that then translates into mechanical delay between the septal and lateral walls. Over the past decade, many studies have examined the pathophysiology of cardiac dyssynchrony, tested the effects of cardiac resynchronization on heart function and energetics,tested the chronic efficacy of this therapy to enhance symptoms and reduce mortality, and better established which patients are most likely to benefit. This brief review discusses these topics.

Management of Heart Failure After Cardiac Resynchronization Therapy

Cardiac resynchronization therapy (CRT) is an established adjunctive treatment for patients with systolic heart failure (HF) and ventricular dyssynchrony. The majority of recipients respond to CRT with improvements in quality of life, New York Heart Association functional class, 6-min walk test, and ventricular function. Management of HF after CRT may include up-titration of neurohormonal blockade and an exercise prescription through cardiac rehabilitation to further improve and sustain clinical outcomes. Diagnostic data provided by the CRT device may help to facilitate and optimize treatment. Initial nonresponder rates remain problematic. We suggest a simple step-by-step management and troubleshooting strategy that integrates device function with advanced HF therapy in patients who do not initially respond to CRT. This algorithm represents a new, comprehensive, collaborative approach between the HF and electrophysiology specialists to further improve and sustain outcomes in the field of CRT.

Echocardiographic Assessment of Ventricular Asynchrony in Dilated Cardiomyopathy and Congenital Heart Disease: Tools and Hopes

Ventricular dyssynchrony is a relatively common problem in patients with heart failure, in particular those with wide QRS complex, and appears to have a deleterious effect on the natural history of heart failure, as it has been associated with increased mortality. Mechanistic studies, observational evaluations, and randomized trials have consistently demonstrated the beneficial effects of cardiac resynchronization therapy (CRT) in patients with moderate-to-severe chronic systolic heart failure and ventricular dyssynchrony who have failed optimal medical treatment. However, despite the promising results, it is estimated that in approximately 30% of patients undergoing CRT, the symptoms of heart failure do not improve or become even worse. One of the most important reasons for this failure is probably the lack of distinct mechanical dyssynchrony before implantation. A number of echocardiographic tools have been developed during the past 3 years for quantitative measurement of the severity of dyssynchrony before and after CRT. This review discusses the actual and potential role of different echocardiographic techniques in selection of patients and optimization of CRT and the value of some new clinical applications such as in congenital heart disease.

Prevalence of mechanical dyssynchrony in patients with heart failure and preserved left ventricular function (a report from the Belgian Multicenter Registry on dyssynchrony)

The present study evaluated the prevalence of mechanical inter- and intraventricular dyssynchrony in patients with heart failure and preserved left ventricular (LV) ejection fraction (LVEF). We studied 138 patients with heart failure (age 67+/-11 years; 76% men); 60 patients had preserved LVEF (>40%). Using conventional Doppler echocardiography, an interventricular mechanical delay>or=40 ms was defined as interventricular dyssynchrony. Using pulse-wave tissue Doppler imaging, the time from the beginning of the QRS complex to onset of systolic motion was measured in 4 basal LV segments. A dispersion of >or=60 ms was defined as intraventricular dyssynchrony. The prevalence of inter- and intraventricular dyssynchrony was lower in patients with preserved LVEF than in those with reduced LVEF (17% vs 41%, p<0.01 for interventricular dyssynchrony, 18% vs 36%, p<0.01 for intraventricular dyssynchrony). However, patients with preserved LVEF and a QRS width>or=120 ms had higher values for the parameters for inter- and intraventricular dyssynchrony than patients with a QRS width<120 ms (interventricular mechanical delay 33+/-20 vs 20+/-16 ms, p<0.05; tissue Doppler imaging dispersion 42+/-26 vs 33+/-22 ms, p<0.05). In patients with a QRS width>or=120 ms, the prevalence of inter- and intraventricular dyssynchrony was comparable for patients with preserved and reduced LVEF (42% vs 55%, p=NS for interventricular dyssynchrony and 45% vs 46%, p=NS for intraventricular dyssynchrony). In conclusion, the prevalence of inter- and intraventricular dyssynchrony was low (17% and 18%, respectively) in patients with heart failure and preserved LVEF. However, in the presence of a QRS width of >or=120 ms, this prevalence increased to almost 50%, comparable to that for patients with heart failure and reduced LVEF and a QRS width of >or=120 ms.

Does a Gender Difference in Response to Cardiac Resynchronization Therapy Exist?

BACKGROUND

Cardiac resynchronization therapy (CRT) has a beneficial effect on clinical symptoms, exercise capacity, and systolic left ventricular (LV) performance in patients with heart failure. The aim of the current study was to evaluate whether a gender difference exists in response to CRT.

METHODS

Consecutive patients with end-stage heart failure (New York Heart Association, NYHA, class III-IV), LV ejection fraction (LVEF) < or =35%, QRS duration >120 ms, and left bundle branch block configuration underwent CRT. At baseline and 6 months post-CRT, clinical and echocardiographic parameters were evaluated; follow-up was obtained up to 5 years. The effects of CRT were compared between women and men.

RESULTS

The study population comprised 137 men and 36 women (mean age 66 +/- 11 years). No differences in baseline characteristics were observed except that nonischemic cardiomyopathy was more frequent in women than men (67% vs 38%, P < 0.05). In all patients, clinical and echocardiographic parameters improved significantly at 6-month follow-up. The magnitude of improvement in different parameters was similar between women and men, e.g., the improvement in NYHA Class was 0.9 +/- 0.6 in women and 1.0 +/- 0.7 in men (NS) and the increase in LVEF was 8 +/- 8% in women as compared to 7 +/- 9% in men (NS). The percentage of individual responders was not different between women and men (76% vs 80%, NS) and 2-year survival was comparable for women and men (84% vs 80%, NS).

CONCLUSION

No gender differences were observed in response to CRT and long-term survival after CRT.

Cardiac resynchronization therapy: the MGH experience

Cardiac resynchronization therapy (CRT) has gained acceptance as a useful form of device therapy for patients with refractory congestive heart failure. Despite recent technical advances, a significant number of patients continue to remain unresponsive to this form of therapy. This article provides an overview of CRT, highlights several unresolved issues and describes ongoing research efforts to address some of these important questions.

Radiographic left ventricular-right ventricular interlead distance predicts the acute hemodynamic response to cardiac resynchronization therapy

Placement of left ventricular (LV) and right ventricular (RV) leads with maximal interlead separation is frequently sought during cardiac resynchronization therapy (CRT), but few published data are available to support this. This study examined the relation between LV and RV lead separation and the acute effects of CRT on cardiac contractility. A total of 51 consecutive patients who underwent CRT for standard indications with sufficient mitral regurgitation for echocardiographic assessment of contractility (using Doppler profiles of mitral regurgitation as a percentage of change in dP/dt [DeltadP/dt] with CRT on and off), successful transvenous LV lead placement, and postprocedural chest radiography were evaluated. The separation of the LV and RV lead tips (direct interlead distance and horizontal and vertical components) was determined on postprocedural posteroanterior and lateral radiographs. The corrected direct LV-RV interlead distance on the lateral radiograph was correlated with the DeltadP/dt (n = 51, r = 0.43, p = 0.002). The lateral interlead distance in the horizontal plane (r = 0.58, p <0.0001), but not the vertical plane (r = -0.28, p = NS), correlated with the DeltadP/dt. The corrected horizontal interlead distance on the lateral film was greater in acute hemodynamic responders to CRT (DeltadP/dt >25%) compared with nonresponders (14.4 +/- 5.4 vs 9.2 +/- 5.8 cm, p = 0.002). Other LV-RV measures on the posteroanterior and lateral radiographs did not correlate with the DeltadP/dt. Use of these findings may help to guide the sites of LV and RV lead placement to maximize the benefit derived from CRT.

Real-Time Three-Dimensional Echocardiography

Background— Left ventricular (LV) mechanical dyssynchrony (LVMD) has emerged as a therapeutic target using cardiac resynchronization therapy (CRT) in selected patients with chronic heart failure. Current methods used to evaluate LVMD are technically difficult and do not assess LVMD of the whole LV simultaneously. We developed and validated real-time 3D echocardiography (RT3DE) as a novel method to assess global LVMD.

Methods and Results— Eighty-nine healthy volunteers and 174 unselected patients referred for routine echocardiography underwent 2D echocardiography and RT3DE. RT3DE data sets provided time-volume analysis for global and segmental LV volumes. A systolic dyssynchrony index (SDI) was derived from the dispersion of time to minimum regional volume for all 16 LV segments. Healthy subjects and patients with normal LV systolic function had highly synchronized segmental function (SDI, 3.5±1.8% and 4.5±2.4%; P =0.7). SDI increased with worsening LV systolic function regardless of QRS duration (mild, 5.4±0.83%; moderate, 10.0±2%; severe LV dysfunction, 15.6±1%; P for trend <0.001). We found that 37% of patients with moderate to severe LV systolic dysfunction had significant dyssynchrony with normal QRS durations (SDI, 14.7±1.2%). Twenty-six patients underwent CRT. At long-term follow-up, responders demonstrated reverse remodeling after CRT with a significant reduction in SDI (16.9±1.1% to 6.9±1%; P <0.0001) and end-diastolic volume (196.6±17.3 to 132.1±13.5 mL; P <0.0001) associated with an increase in LV ejection fraction (17±2.2% to 31.6±2.9%; P <0.0001).

Conclusions— RT3DE can quantify global LVMD in patients with and without QRS prolongation. RT3DE represents a novel technique to identify chronic heart failure patients who may otherwise not be considered for CRT.

Effect of Cardiac Resynchronization Therapy on Left Ventricular Diastolic Filling Pattern in Responder and Nonresponder Patients

BACKGROUND

The aim of this study was to investigate the short- and long-term effects of cardiac resynchronization therapy (CRT) on left ventricular (LV) diastolic filling pattern and the relation between the diastolic filling pattern and the response to CRT.

METHODS

Twenty-three patients with systolic heart failure and complete left bundle-branch block underwent implantation of biventricular pacemaker devices. In order to follow the changes in diastolic function, mitral inflow, pulmonary venous flow, and LV flow propagation (Vp) velocities were measured with pulsed-wave and color M-mode Doppler echocardiography 1 week before and 1 and 6 months after pacemaker implantation. At the 6-month follow-up, patients were divided into two groups according to their response to CRT defined as a relative increase in LV ejection fraction (LVEF) > or =25% versus baseline.

RESULTS

After biventricular pacemaker implantation, significant clinical improvement was observed in all patients. Compared to baseline, the ratio of early-to-late peak velocities (E/A) decreased significantly at the 6th month (E/A ratio: from 1.5 +/- 0.9 to 0.8 +/- 0.5 at the 6th month (P = 0.02)). Pulmonary systolic flow to diastolic flow ratio (PVs/PVd) increased with CRT after 6 months (PVs/PVd ratio: from 0.9 +/- 0.4 to 1.3 +/- 0.7 at the 6th month (P = 0.02)). E/Vp ratio decreased significantly at the 1st and 6th month (E/Vp ratio: from 2.7 +/- 0.8 to 2 +/- 0.8 at the 1st (P < 0.002) and to 1.9 +/- 0.7 at the 6th month (P < 0.02)). In responders (n: 17, 74%), E wave and PVra velocity decreased, E-wave deceleration time increased, and E/Vp ratio improved significantly, whereas in nonresponders, changes in LV diastolic parameters remained insignificant. However, diastolic filling pattern improved significantly at the 1st and 6th month of CRT in both responders and nonresponders.

CONCLUSION

CRT enhances diastolic filling patterns in both responder and nonresponder patients. This may be related to improvement in symptoms even in nonresponders who have a relative increase in LVEF <25%.

Utility of echocardiographic radial strain imaging to quantify left ventricular dyssynchrony and predict acute response to cardiac resynchronization therapy

Echocardiographic strain imaging was used to quantify radial mechanical dyssynchrony in 38 patients who underwent cardiac resynchronization therapy. Dyssynchrony, defined as the time difference of peak radial strain in the septum versus the posterior wall, was significantly greater in patients with acute hemodynamic responses, and changes in radial dyssynchrony correlated with changes in stroke volume. A > or =130-ms difference in septal versus posterior wall peak strain when combined with a favorable left ventricular lead position was strongly predictive of immediate improvement in stroke volume with resynchronization therapy (95% sensitivity, 88% specificity), regardless of electrocardiographic QRS duration.

[Effect of CRT on morbidity and mortality]

Patients with chronic heart failure who show a left ventricular ejection fraction < or =35% and remain in NYHA class III or IV despite optimal pharmacologic treatment show less morbidity and mortality on cardiac resynchronization therapy (CRT) if the left ventricle shows asynchrony. Although only one study has shown a significant reduction of mortality about 4% less deaths per year in the first two years can be resumed. Procedure related mortality is less than 1%. By improving on average one NYHA class 10-20% less patients experience hospitalization due to heart failure in the first two years after implantation of a CRT device. Patients who are hospitalized despite CRT have on average a hospital stay below 5 days. At least 10% of patients are currently suffering surgical revisions due to infections, dislocations and high pacing thresholds of the left ventricular lead. If costs saved by less hospitalization can finance costs of CRT or even exceed the costs of CRT remains unknown.

[Improved identification of suitable patients for cardiac resynchronization therapy by transthoracic echocardiography]

Transthoracic echocardiography provides numerous options for the evaluation and quantification of contractile cardiac asynchrony in patients with advanced heart failure. Important information on the presence of asynchrony can be obtained already during a standard routine examination with conventional techniques (2D, M-mode and Doppler). Newer techniques such as tissue Doppler imaging and real-time 3D-echocardiography enable us to better quantify the degree of asynchrony. The following article describes the echocardiographic features of asynchrony and algorithms for the improved identification of suitable patients for cardiac resynchronization therapy.

[Improved analysis of left ventricular function using three-dimensional echocardiography]

Left ventricular geometry and function are important pathophysiologic and prognostic parameters. However, especially in patients with cardiac pathologies left ventricular geometry can be complex. Quantification of left ventricular volumes using conventional two-dimensional echocardiography is only possible when simplifying assumptions of left ventricular geometry are made. In contrast three-dimensional echocardiography allows direct quantification of left ventricular volumes even in complex distortions of left ventricular shape. The availability of real-time three-dimensional echocardiography has brought this technique into clinical practice. Three-dimensional echocardiography is a technique that may be used as a routine echocardiographic method in the near future.