Effect of external counterpulsation on cardiac work following cardiac surgery: implications of the mechanism responsible for clinical benefits

Hemodynamics of ventricular-arterial coupling under enhanced external counterpulsation: An optimized dual-source lumped parameter model

BACKGROUND AND OBJECTIVE

Enhanced external counterpulsation (EECP) is a mechanically assisted circulation technique widely used in the rehabilitation and management of ischemic cardiovascular diseases. It contributes to cardiovascular functions by regulating the afterload of ventricle to improve hemodynamic effects, including increased diastolic blood pressure at aortic root, increased cardiac output and enhanced blood perfusion to multiple organs including coronary circulation. However, the effects of EECP on the coupling of the ventricle and the arterial system, termed ventricular-arterial coupling (VAC), remain elusive. We aimed to investigate the acute effect of EECP on the dynamic interaction between the left ventricle and its afterload of the arterial system from the perspective of ventricular output work.

METHODS

A neural network assisted optimization algorithm was proposed to identify the ordinary differential equation (ODE) relation between aortic root blood pressure and flow rate. Based on the optimized order of ODE, a lumped parameter model (LPM) under EECP was developed taking into consideration of the simultaneous action of cardiac and EECP pressure sources. The ventricular output work, in terms of aortic pressure and flow rate cooperated with the LPM, was used to characterize the VAC of ventricle and its afterload. The VAC subjected to the principle of minimal ventricular output work was validated by solving the Euler-Poisson equation of cost function, ultimately determining the waveforms of aortic pressure and flow rate.

RESULTS

A third-order ODE can precisely describe the hemodynamic relationship between aortic pressure and flow rate. An optimized dual-source LPM with three energy-storage elements has been constructed, showing the potential in probing VAC under EECP. The LPM simulation results demonstrated that the VAC in terms of aortic pressure and flow rate yielded to the minimal ventricular output work under different EECP pressures.

CONCLUSIONS

The ventricular-arterial coupling under EECP is subjected to the minimal ventricular output work, which can serve as a criterion for determining aortic pressure and flow rate. This study provides insight for the understanding of VAC and has the potential in characterizing the performance of the ventricular and arterial system under EECP.

Effect of External Counterpulsation on Running Performance and Perceived Recovery

PURPOSE

To determine the efficacy of 20 minutes of external counterpulsation (ECP) on subsequent 1.2-km shuttle run test (1.2SRT) performance and perceived recovery following fatiguing high-intensity exercise.

METHODS

After familiarization, 13 recreationally active males (21.4 [1.9] y) participated in 2 experimental trials in a randomized crossover design. At 8:00 AM, participants completed a 1.2SRT, followed by an individualized high-intensity exercise bout and 20 minutes of ECP or supine passive rest (control). At 2:00 PM a second 1.2SRT was completed. Completion time for 1.2SRT (measured in seconds), heart rate, and Borg rating of perceived exertion were compared across conditions. Total quality of recovery and 100-mm visual analogue scale of perceived benefit of recovery were assessed at multiple time points.

RESULTS

A significantly smaller decline in PM 1.2SRT completion time compared with AM (baseline) was found for ECP compared with control (P = .008; moderate, very likely beneficial effect size of -0.77 [-1.53 to 0.05]). Total quality of recovery was significantly higher for ECP than control (P < .001), and perceived benefit of recovery was higher following ECP (P < .001, very large, most likely beneficial effect size of 2.08 [1.22 to 2.81]).

CONCLUSIONS

Twenty minutes of ECP was found to be an effective recovery modality for within-day, between-bouts exercise, positively influencing subsequent 1.2SRT performance and enhancing perceptual recovery. ECP may be applied as a viable alternative to optimize and accelerate the recovery process, particularly in the event of congested training or competition demands.

External Counterpulsation Reduces Beat-to-Beat Blood Pressure Variability When Augmenting Blood Pressure and Cerebral Blood Flow in Ischemic Stroke

BACKGROUND AND PURPOSE

External counterpulsation (ECP) is a noninvasive method used to enhance cerebral perfusion by elevating the blood pressure in ischemic stroke. However, the response of the beat-to-beat blood pressure variability (BPV) in ischemic stroke patients during ECP remains unknown.

METHODS

We enrolled recent ischemic stroke patients and healthy controls. Changes in the blood flow velocities in bilateral middle cerebral arteries and the continuous beat-to-beat blood pressure before, during, and after ECP were monitored. Power spectral analysis revealed that the BPV included oscillations at very low frequency (VLF; <0.04 Hz), low frequency (LF; 0.04-0.15 Hz), and high frequency (HF; 0.15-0.40 Hz), and the total power spectral density (TP; <0.40 Hz) and LF/HF ratio were calculated.

RESULTS

We found that ECP significantly increased the systolic and diastolic blood pressures in both stroke patients and controls. ECP decreased markedly the systolic and diastolic BPVs at VLF and LF and the TP, and the diastolic BPV at HF when compared with baseline. The decreases in diastolic and systolic BPV reached 37.56% and 23.20%, respectively, at VLF, 21.15% and 12.19% at LF, 8.76% and 16.59% at HF, and 31.92% and 23.62% for the total TP in stroke patients, which did not differ from those in healthy controls. The change in flow velocity on the contralateral side was positively correlated with the total TP systolic BPV change induced by ECP (r=0.312, p=0.035).

CONCLUSIONS

ECP reduces the beat-to-beat BPV when increasing the blood pressure and cerebral blood flow velocity in ischemic stroke patients. ECP might be able to improve the clinical outcome by decreasing the beat-to-beat BPV in stroke patients, and this should be explored further in future studies.

Novel external counterpulsation system, compact counterpulsation, was effective to treat severe ischemic heart failure: a case report

Compact counterpulsation (CP) is a novel external counterpulsation system. The preoperative clinical utility of compact CP therapy in patients has not been established. In the present report, we describe a case wherein compact CP therapy was successfully used to treat severe ischemic heart failure. A 70-year-old man was diagnosed with ischemic heart disease and mitral valve regurgitation at 61 years of age. Therefore, he underwent coronary artery bypass and mitral valve plasty. The patient's condition started to gradually deteriorate at 68 years of age, and he became progressively dependent on catecholamine support. Mitral valve regurgitation recurred, which caused worsening of heart function. Before a mitral valve replacement, the patient had been treated with compact CP therapy to improve heart function and general condition. The patient's clinical condition improved with compact CP therapy after only ten sessions; in addition, he could be weaned off catecholamine support. No adverse effects were observed, and therefore, he could complete the CP therapy as an outpatient. Mitral valve replacement was performed after a total of 44 sessions. The patient had an uneventful postoperative course and was discharged on the 18th postoperative day. Compact CP therapy was thus performed on our patient without any discomfort and appears to be an effective treatment for patients with severe ischemic heart failure.