Radial Artery Tonometry for Biv Pacemaker Optimization
Radial Artery Tonometry for Biv 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.
Prolongation of the pre-ejection period (PEP) and shortening of ejection time (ET) is the principal abnormality in systolic heart failure (HF) patients with reduced left ventricular ejection fraction (LVEF). PEP is comprised of electromechanical delay (EMD) and isovolumic contraction time(IVCT). PEP/LVET is a validated measurement of LV systolic performance and is independent of heart rate. Myocardial performance index (MPI) is a combined measure of systolic and diastolic dysfunction, which indicates the non-effective fraction and has been widely used to estimate LV function and predict the prognosis in HF patients.
Cardiac resynchronization therapy (CRT) also referred to as atrial-synchronous biventricular (Biv) pacing, has been an effective treatment for medically refractory HF patients with ventricular dyssynchrony. It is able to shorten PEP, lengthen ET and reduce MPI thus leading to an increase in LV effective fraction and stoke volume. Thus PEP, ET and MPI have been regarded as the primary parameters to guide pacemaker optimization. Maximum hemodynamic improvement occurs at an AV delay (AVD) that provides the most favorable preload and an interventricular delay (VVD) that exhibits minimal dyssynchrony, the longest ET and the shortest PEP for a dilated and failing heart.
In current practice, despite careful selection, as many as 30–40% of patients do not respond to, or even deteriorate after CRT. An important reason for such high non-responder rate is lack of individual patient pacemaker optimization. Echocardiography has been the most recognized method for pacemaker optimization and is endorsed by recent guidelines from American Society of Echocardiography and European Society of Cardiology. It has been shown to improve cardiac output, reduce hospitalization rates and improve New York Heart Association (NYHA) class in HF patients. Measurement of IVCT is not feasible by echo and MPI measurement which requires simultaneous assessment of mitral inflow and aortic outflow is difficult to obtain during online evaluation. LV outflow velocity time integral (VTI) measurement is more reliable, however difficult to obtain due to changes in sample volume positioning. Assessment of multiple Doppler parameters such as LV filling and ejection as well as other Doppler parameters makes the procedure more reliable however also makes it more time and labor intensive. Furthermore it requires advanced skill in echo Doppler and need for multispecialty collaboration leading to underutilization of echo Doppler for pacemaker optimization. Thus methods that are simple and accurate for assisting echo Doppler techniques or better still be usable as stand-alone methods may lead to a wider adoption of pacemaker optimization.
We have recently shown the utility of phonocardiographic S3 intensity in guiding pacemaker optimization, however the technique appears to work best in those with baseline S3 of > 5. The maximal dP/dt of the radial pulse appears to be a valuable and reproducible peripheral criterion of LV systolic performance in heart failure. In recent studies we have demonstrated the potential value of ejection time measured by radial artery tonometry in patients undergoing Biv pacemaker optimization. Recent enhancement with a wrist-band tonometer instead of a hand held pen-like device allows a hand-free operation and capture of radial artery waveform without the variability associated with the examiner hand motion. In addition the device now allows an easy and quick assessment of PEP through computerized analysis of a characteristic point ("foot of the wave" or "timing point") on the transcutaneous radial artery waveform and the ECG-Q wave averaged approximately 10 cardiac cycles. This value comprises of two components, PEP of aortic waveform and the travel time of the pressure wave from heart to radial artery that remains constant in each patient.
We hypothesized that PEP by radial artery tonometry may correspond with ET and VTI by echo and may be used during Biv pacemaker optimization. This study was designed to investigate the relationship of PEP measurement by radial artery tonometry with echo derived ET and LV VTI, during Biv pacemaker optimization.
Abstract and Introduction
Abstract
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.
Introduction
Prolongation of the pre-ejection period (PEP) and shortening of ejection time (ET) is the principal abnormality in systolic heart failure (HF) patients with reduced left ventricular ejection fraction (LVEF). PEP is comprised of electromechanical delay (EMD) and isovolumic contraction time(IVCT). PEP/LVET is a validated measurement of LV systolic performance and is independent of heart rate. Myocardial performance index (MPI) is a combined measure of systolic and diastolic dysfunction, which indicates the non-effective fraction and has been widely used to estimate LV function and predict the prognosis in HF patients.
Cardiac resynchronization therapy (CRT) also referred to as atrial-synchronous biventricular (Biv) pacing, has been an effective treatment for medically refractory HF patients with ventricular dyssynchrony. It is able to shorten PEP, lengthen ET and reduce MPI thus leading to an increase in LV effective fraction and stoke volume. Thus PEP, ET and MPI have been regarded as the primary parameters to guide pacemaker optimization. Maximum hemodynamic improvement occurs at an AV delay (AVD) that provides the most favorable preload and an interventricular delay (VVD) that exhibits minimal dyssynchrony, the longest ET and the shortest PEP for a dilated and failing heart.
In current practice, despite careful selection, as many as 30–40% of patients do not respond to, or even deteriorate after CRT. An important reason for such high non-responder rate is lack of individual patient pacemaker optimization. Echocardiography has been the most recognized method for pacemaker optimization and is endorsed by recent guidelines from American Society of Echocardiography and European Society of Cardiology. It has been shown to improve cardiac output, reduce hospitalization rates and improve New York Heart Association (NYHA) class in HF patients. Measurement of IVCT is not feasible by echo and MPI measurement which requires simultaneous assessment of mitral inflow and aortic outflow is difficult to obtain during online evaluation. LV outflow velocity time integral (VTI) measurement is more reliable, however difficult to obtain due to changes in sample volume positioning. Assessment of multiple Doppler parameters such as LV filling and ejection as well as other Doppler parameters makes the procedure more reliable however also makes it more time and labor intensive. Furthermore it requires advanced skill in echo Doppler and need for multispecialty collaboration leading to underutilization of echo Doppler for pacemaker optimization. Thus methods that are simple and accurate for assisting echo Doppler techniques or better still be usable as stand-alone methods may lead to a wider adoption of pacemaker optimization.
We have recently shown the utility of phonocardiographic S3 intensity in guiding pacemaker optimization, however the technique appears to work best in those with baseline S3 of > 5. The maximal dP/dt of the radial pulse appears to be a valuable and reproducible peripheral criterion of LV systolic performance in heart failure. In recent studies we have demonstrated the potential value of ejection time measured by radial artery tonometry in patients undergoing Biv pacemaker optimization. Recent enhancement with a wrist-band tonometer instead of a hand held pen-like device allows a hand-free operation and capture of radial artery waveform without the variability associated with the examiner hand motion. In addition the device now allows an easy and quick assessment of PEP through computerized analysis of a characteristic point ("foot of the wave" or "timing point") on the transcutaneous radial artery waveform and the ECG-Q wave averaged approximately 10 cardiac cycles. This value comprises of two components, PEP of aortic waveform and the travel time of the pressure wave from heart to radial artery that remains constant in each patient.
We hypothesized that PEP by radial artery tonometry may correspond with ET and VTI by echo and may be used during Biv pacemaker optimization. This study was designed to investigate the relationship of PEP measurement by radial artery tonometry with echo derived ET and LV VTI, during Biv pacemaker optimization.
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