Time intervals of cardiac resynchronization therapy in heart failure

Comparison of the measured pre-ejection periods and left ventricular ejection times between echocardiography and impedance cardiography for optimizing cardiac resynchronization therapy

BACKGROUND

The pre-ejection period (PEP) and left ventricular ejection time (LVET) are easily measured by impedance cardiography (ICG). We hypothesized that the PEP/LVET measured by ICG would correlate with that measured by echocardiography, and that PEP/LVET measured by ICG would be useful for cardiac resynchronization therapy (CRT) optimization.

METHODS

Newly CRT implanted patients were optimized by echocardiography. The PEP/LVET was measured by echocardiography and ICG in two different settings: optimized setting and right ventricle (RV)-only pacing.

RESULTS

The PEP/LVET was significantly decreased in the optimized setting compared with that in RV-only pacing (0.62±0.13 vs 0.75±0.16, p<0.05). The PEP/LVET values calculated by ICG and echocardiography were positively correlated (r=0.553, p=0.003).

CONCLUSION

ICG was useful for the optimization of CRT.

Pre-ejection period by radial artery tonometry supplements echo Doppler findings during biventricular pacemaker optimization

Background

Biventricular (Biv) pacemaker echo optimization has been shown to improve cardiac output however is not routinely used due to its complexity. We investigated the role of a simple method involving computerized pre-ejection time (PEP) assessment by radial artery tonometry in guiding Biv pacemaker optimization.

Methods

Blinded echo and radial artery tonometry were performed simultaneously in 37 patients, age 69.1 ± 12.8 years, left ventricular (LV) ejection fraction (EF) 33 ± 10%, during Biv pacemaker optimization. Effect of optimization on echo derived velocity time integral (VTI), ejection time (ET), myocardial performance index (MPI), radial artery tonometry derived PEP and echo-radial artery tonometry derived PEP/VTI and PEP/ET indices was evaluated.

Results

Significant improvement post optimization was achieved in LV ET (286.9 ± 37.3 to 299 ± 34.6 ms, p < 0.001), LV VTI (15.9 ± 4.8 cm to 18.4 ± 5.1 cm, p < 0.001) and MPI (0.57 ± 0.2 to 0.45 ± 0.13, p < 0.001) and in PEP (246.7 ± 36.1 ms to 234.7 ± 35.5 ms, p = 0.003), PEP/ET (0.88 ± 0.21 to 0.79 ± 0.17, p < 0.001), and PEP/VTI (17.3 ± 7 to 13.78 ± 4.7, p < 0.001). The correlation between comprehensive echo Doppler and radial artery tonometry-PEP guided optimal atrioventricular delay (AVD) and optimal interventricular delay (VVD) was 0.75 (p < 0.001) and 0.69 (p < 0.001) respectively. In 29 patients with follow up assessment, New York Heart Association (NYHA) class reduced from 2.5 ± 0.8 to 2.0 ± 0.9 (p = 0.004) at 1.8 ± 1.4 months.

Conclusion

An acute shortening of PEP by radial artery tonometry occurs post Biv pacemaker optimization and correlates with improvement in hemodynamics by echo Doppler and may provide a cost-efficient approach to assist with Biv pacemaker echo optimization.

Electromechanical activation time in the prediction of discharge outcomes in patients hospitalized with acute heart failure syndrome

OBJECTIVE

Left ventricular systolic time intervals, including pre-ejection period (PEP), ejection time (ET), and their ratio (PEP/ET), is determined by systolic and diastolic function and ventriculo-arterial coupling. We investigated the usefulness of the electromechanical activation time [(EMAT) PEP minus isovolumic contraction time] in the prediction of cardiac mortality or re-hospitalization for heart failure in patients with the acute heart failure syndrome (AHFS).

PATIENTS AND METHODS

A total of 45 patients (71.9±16.1 years old) hospitalized for AHFS were enrolled. Systolic time intervals and EMAT normalized by cardiac cycle length (%) were measured separately by separate automated acoustic devices. All parameters were assessed within 24 hours of admission, before discharge, and 2 weeks after discharge.

RESULTS

During a mean follow-up of 242±156 days, 20 patients (44%) incurred adverse cardiovascular events including 18 re-hospitalizations for heart failure and 2 cardiovascular deaths. Using uni-variate Cox regression analysis, at admission %EMAT and %PEP, pre-discharge %EMAT, and post-discharge %EMAT significantly predicted post-discharge cardiovascular events with hazard ratios and 95% confidence intervals of 1.75 (1.13-2.70), 1.67 (1.02-2.70), 1.87 (1.10-3.17) and 2.50 (1.58-3.97) per 1-SD increment, respectively. The predictions remained significant after adjustment for age, sex, left ventricular ejection fraction, E/E´ by Doppler echocardiography, and serum N-terminal pro-brain natriuretic peptide.

CONCLUSION

EMAT measured during the hospitalization course is useful in the prediction of cardiovascular outcomes in patients with AHFS independent of left ventricular ejection fraction, E/E´, and serum N-terminal pro-brain natriuretic peptide.

Hemodynamic correlates of the third heart sound and systolic time intervals

Bedside diagnostic tools remain important in the care of patients with heart failure. Over the past two centuries, cardiac auscultation and phonocardiography have been essential in understanding cardiac pathophysiology and caring for patients with heart disease. Diastolic heart sounds (S3 and S4) and systolic time intervals have been particularly useful in this regard. Unfortunately, auscultation skills have declined considerably, and systolic time intervals have traditionally required carotid pulse tracings. Newer technology allows the automated detection of heart sounds and measurement of systolic time intervals in a simple, inexpensive, noninvasive system. Using the newer system, the authors present data on the hemodynamic correlates of the S3 and abnormal systolic time intervals. These data serve as the foundation for using the system to better understand the test characteristics and pathophysiology of the S3 and systolic time intervals, and help to define their use in improving the bedside diagnosis and management of patients with heart failure.

Acoustic cardiographic parameters and their relationship to invasive hemodynamic measurements in patients with left ventricular systolic dysfunction

Data obtained at cardiac catheterization were used to evaluate the utility of acoustic cardiographic data in assessing the hemodynamic abnormalities associated with left ventricular systolic dysfunction (LVSD). Thirty-seven patients (mean age, 62.6 years) underwent catheterization, and hemodynamic data were recorded. Acoustic cardiographic recordings were obtained using a system that records and algorithmically interprets diastolic heart sounds and parameters analogous to traditional systolic time intervals. Seventeen patients had LVSD (defined as ejection fraction <50%). The 17 patients with LVSD composed the cohort for analysis. There were strong associations between acoustic cardiographic parameters and left ventricular end-diastolic pressure, ejection fraction, and maximum contractility. Heart rate tended to influence the strength of these correlations. The authors conclude that acoustic cardiographic data can be used in the evaluation of patients with known or suspected LVSD, and specifically in the selection of patients for cardiac resynchronization therapy and the optimization of the settings of implanted resynchronization devices.

Usefulness of systolic time intervals in the identification of abnormal ventriculo-arterial coupling in stable heart failure patients

BACKGROUND

The ratio of effective arterial elastance (Ea) to ventricular end-systolic elastance (Ees) indicates the status of ventriculo-arterial coupling.

AIMS

We investigated if systolic time intervals (pre-ejection period, PEP; ejection time, ET; and their ratio, PEP/ET) can be used to identify heart failure patients with abnormal ventriculo-arterial coupling.

METHODS

Age and sex-matched study subjects included 54 apparently healthy subjects with normal left ventricular (LV) function, and stable patients with LV diastolic (n=54) and systolic dysfunction (n=54). Ees and Ea were estimated non-invasively by echocardiography, and abnormal ventriculo-arterial coupling was defined as Ea/Ees>1.2. PEP, ET, and PEP/ET were measured automatically using electrocardiography, phonocardiography, and brachial pulse volume recording.

RESULTS

Ea/Ees>1.2 was present in 48.1% of subjects with systolic dysfunction. The PEP/ET was significantly associated with most parameters of LV structure and function, and Ea/Ees (r=0.67, p<0.001). Using PEP/ET> or =0.423 as cut point, the sensitivity and specificity to identify patients with Ea/Ees>1.2 were 85.7% and 84.3%, respectively for the whole population, and 84.6% and 78.6%, for patients with systolic dysfunction.

CONCLUSION

Abnormal ventriculo-arterial coupling was present in almost half of stable patients with systolic dysfunction. PEP/ET was useful in identifying such patients.

Measurement of QRS duration for biventricular pacing optimization

Optimization of left ventricular pacing site or interventricular pacing delay improves the efficacy of biventricular pacing (BiVP). Cardiac output (CO) based optimization, however, is invasive and slow. QRS duration (QRSd) is noninvasive and responds rapidly. Accordingly, we investigated the utility of QRSd for BiVP optimization in a model of acute right ventricular (RV) pressure overload. In seven anesthetized open-chest pigs, BiVP was implemented with right atrial and RV pacing wires. A 6-electrode array was placed behind the LV. Heart block was established by alcohol ablation. The pulmonary artery was snared to double peak RV pressure. Fifty-four combinations of left ventricular pacing site and interventricular pacing delay were tested in random order over 30-second intervals. QRSd was assessed from electrocardiogram lead II, CO from aortic flow probe, and ventricular function from micromanometers. Comparisons were made with the Pearson's correlation coefficient (r). QRSd narrowing was associated with improved RV function and transseptal synchrony, but correlation with CO was poor. Additionally, QRSd averaged over the last 20 cardiac cycles in each interval was compared with values averaged over successive cardiac cycles following each reprogramming. Seven cardiac cycles after reprogramming, the average r-value went above 0.90 and plateaued. QRSd-based optimization merits further study during BiVP in patients with congestive heart failure.

Accelerometer-derived time intervals during various pacing modes in patients with biventricular pacemakers: comparison with normals

INTRODUCTION

Changes due to biventricular pacing have been documented by shortening of QRS duration and echocardiography. Compared to normal ventricular activation, the presence of left bundle branch block (LBBB) results in a significant change in cardiac cycle time intervals. Some of these have been used to quantify the underlying cardiac dyssynchrony, assess the effects of biventricular pacing, and guide programming of ventricular pacing devices. This study evaluates a simple noninvasive method using accelerometers attached to the skin to measure cardiac time intervals in biventricularly paced patients.

METHODS

Ten patients with biventricular pacemakers previously implanted for congestive heart failure were paced in the AAI mode, then in atrioventricular (AV) sequential mode from the right and left ventricles followed by biventricular pacing. Simultaneous recordings were obtained by 2D, Doppler echocardiography as well as by accelerometers. Similar recordings were obtained from 10 gender, aged matched, normal controls during sinus rhythm.

RESULTS

Compared to normals, heart failure patients paced in AAI mode had prolonged isovolumetric contraction time (IVCT), shorter ventricular ejection time (LVET), and prolonged isovolumetric relaxation (IVRT). With biventricular pacing the IVCT decreased, but the LVET and IVRT did not change significantly. There was excellent correlation between the echo and accelerometer-measured intervals.

CONCLUSIONS

Shortening of the IVCT measured by an accelerometer is a consistent time interval change due to biventricular pacing that probably reflects more rapid acceleration of left ventricular ejection. The accelerometer may be useful to assess immediate efficacy of biventricular pacing during device implantation and optimize programmable time intervals such as AV and interventricular (VV) delays.

Systolic Dysfunction: Correlation of Acoustic Cardiography With Doppler Echocardiography

For detection of left ventricular (LV) systolic dysfunction in the outpatient setting, simultaneous electrocardiographic and heart sound data have been shown to be helpful. In 161 patients with suspected or known cardiac disease, echocardiography and acoustic cardiography were performed. Acoustic cardiographic parameters correlated to echocardiography included: presence or absence of S3, electromechanical activation time (EMAT), LV systolic time (LVST), and EMAT/LVST. LV ejection fraction was >or=50% in 82 patients (S3 present in 9.8%) and <50% in 79 patients (S3 present in 30.4%; the <50% group also had a greater EMAT, EMAT/LVST, and lower mean LVST [p<0.05]). Patients with an S3 had a lower ejection fraction, larger mean left atrial and LV dimensions, and an increased proportion of diastolic dysfunction. Acoustic cardiography allows reliable detection of the S3, which correlates with echocardiographic evidence of impaired LV function, and the EMAT/LVST ratio reflects reduced ejection fraction, providing an affordable, accessible means to assess LV dysfunction in the outpatient setting.

Cardiac Resynchronization Therapy and the Emerging Role of Echocardiography (Part 2): The Comprehensive Examination

Cardiac resynchronization therapy has been established as an adjunctive treatment for patients with severe left ventricular systolic dysfunction and medically refractory heart failure symptoms with a prolonged electrocardiographic QRS interval. Echocardiography has emerged as a useful method to evaluate patients who are considered for cardiac resynchronization therapy. This review outlines measurements of ventricular performance to be used in this patient population including echocardiographic optimization of cardiac resynchronization therapy device settings.

Renewed Interest in Preejectional Isovolumic Phase: New Applications of Tissue Doppler Indexes: Implications to Ventricular Dyssynchrony

There is renewed interest in isovolumic contraction (IC) in tissue Doppler echocardiography of the myocardial walls, which is revisited in this editorial with new regional velocity data. The aims are to recall traditional background information and to emphasize the need to master the rapidly evolving tissue Doppler procedures for the accurate display of brief IC. IC, a preejectional component of great physiologic interest, is very demanding in terms of ultrasound technology. The onset and end of its motion velocities should be unambiguously defined versus the QRS complex and ejection wall motion. This is a prerequisite for exploiting the new information as guidance toward new therapeutic strategies from a practical viewpoint. However, IC preload dependence should be kept in mind, because of its limited potential for contractility studies. Finally, when only duration measurements are made in the assessment of ventricular dyssynchrony, regional preejectional duration is the pertinent tool to single out the onset of ejection local wall motion.