Sequential external counterpulsation increases cerebral and renal blood flow

Deep-learning-based real-time individualization for reduce-order haemodynamic model

The reduced-order lumped parameter model (LPM) has great computational efficiency in real-time numerical simulations of haemodynamics but is limited by the accuracy of patient-specific computation. This study proposed a method to achieve the individual LPM modeling with high accuracy to improve the practical clinical applicability of LPM. Clinical data was collected from two medical centres comprising haemodynamic indicators from 323 individuals, including brachial artery pressure waveforms, cardiac output data, and internal carotid artery flow waveforms. The data were expanded to 5000 synthesised cases that all fell within the physiological range of each indicator. LPM of the human blood circulation system was established. A double-path neural network (DPNN) was designed to input the waveforms of each haemodynamic indicator and their key features and then output the individual parameters of the LPM, which was labelled using a conventional optimization algorithm. Clinically collected data from the other 100 cases were used as the test set to verify the accuracy of the individual LPM parameters predicted by DPNN. The results show that DPNN provided good convergence in the training process. In the test set, compared with clinical measurements, the mean differences between each haemodynamic indicator and the estimate calculated by the individual LPM based on the DPNN were about 10 %. Furthermore, DPNN prediction only takes 4 s for 100 cases. The DPNN proposed in this study permits real-time and accurate individualization of LPM's. When facing medical issues involving haemodynamics, it lays the foundation for patient-specific numerical simulation, which may be beneficial for potential clinical application.

Enhanced external counterpulsation, focusing on its effect on kidney function, and utilization in patients with kidney diseases: a systematic review

Background

Enhanced external counterpulsation (EECP) is provided by a noninvasive device positively affecting cardiovascular function via mechanisms called diastolic augmentation and systolic unloading. The renal aspects of EECP therapy have not been extensively investigated.

Objectives

To assess the effect of EECP on renal function and to determine the application in patients with kidney disease.

Methods

MEDLINE, EMBASE, SCOPUS, and Cochrane CENTRAL databases were searched for all studies involving EECP treatments. The title and abstract of all searched literatures were screened, and those focusing on renal outcome or conducting in kidney disease patients were selected.

Results

Eight studies were included in the qualitative analysis. EECP increases stroke volume, mean arterial pressure, renal artery blood flow, renal plasma flow, glomerular filtration rate (GFR), plasma atrial natriuretic peptide, urine volume, and urinary sodium chloride excretion, but reduces the plasma concentration of renin and endothelin-1 in healthy subjects. A single session of EECP after radioactive contrast exposure could provide increased contrast clearance, and this reduces contrast-induced kidney injury in patients, irrespective of previous kidney function. Thirty-five-hour sessions of EECP treatment were illustrated to increase long-term estimated GFR in patients with chronic angina and heart failure. In cirrhotic patients, EECP fails to improve GFR and renal vascular resistance. EECP device could maintain blood pressure, decrease angina symptoms, and increase cardiac perfusion in hemodialysis patients.

Conclusion

EECP treatment potentially increases renal perfusion and prevents kidney injury in several conditions. EECP possibly provides beneficial effects on hemodynamics and cardiac function in hemodialysis patients.

Cerebral multi-autoregulation model based enhanced external counterpulsation treatment planning for cerebral ischemic stroke

Enhanced external counterpulsation (EECP) treatment for cerebral ischemic stroke patients with differing severity of stenosis, is subject to uncertainties due to the varying effects of the cerebral autoregulation mechanism on haemodynamics. The current study reports the development of a cerebral multi-autoregulation (MR) mathematical model, based on cerebral arteriole regulation of neurogenic, vascular smooth muscle reflex and shear stress mechanisms which takes into account the severity of stenosis. The model was evaluated by comparison to authentic clinical measurements of cerebral autoregulatory efficiency. Then it was applied to a 0D/3D geometric multi-scale haemodynamic model of a cerebral artery. Haemodynamic indicators were calculated under different pressurization durations of EECP to evaluate the efficacy for different stenosis lesions. Moderate stenosis of 50% to 60% produced excessive time-averaged wall shear stress in the distal area of the stenosis (>7 Pa) during prolonged pressurization and may result in damage to vascular endothelial cells. However, prolonged pressurization did not result in haemodynamic risk for severe stenosis of 70% to 80%, indicating that the duration of pressurization may be extended with increasing severity of stenosis. The current MR model accurately simulated cerebral blood flow and has relevance to the simulation of cerebral haemodynamics in a clinical setting.

Treatment strategy of different enhanced external counterpulsation frequencies for coronary heart disease and cerebral ischemic stroke: A hemodynamic numerical simulation study

BACKGROUND AND OBJECTIVES

Currently, enhanced external counterpulsation (EECP) devices mainly produce one counterpulsation per cardiac cycle. However, the effect of other frequencies of EECP on the hemodynamics of coronary and cerebral arteries is still unclear. It should be investigated whether one counterpulsation per cardiac cycle leads to the optimal therapeutic effect in patients with different clinical indications. Therefore, we measured the effects of different frequencies of EECP on the hemodynamics of coronary and cerebral arteries to determine the optimal counterpulsation frequency for the treatment of coronary heart disease and cerebral ischemic stroke.

METHODS

We established 0D/3D geometric multi-scale hemodynamics model of coronary and cerebral arteries in two healthy individuals, and performed clinical trials of EECP to verify the accuracy of the multi-scale hemodynamics model. The pressure amplitude (35 kPa) and pressurization duration (0.6 s) were fixed. The global and local hemodynamics of coronary and cerebral arteries were studied by changing counterpulsation frequency. Three frequency modes, including one counterpulsation in one, two and three cardiac cycles, were applied. Global hemodynamic indicators included diastolic / systolic blood pressure (D/S), mean arterial pressure (MAP), coronary artery flow (CAF), and cerebral blood flow (CBF), whereas local hemodynamic effects included area-time-averaged wall shear stress (ATAWSS) and oscillatory shear index (OSI). The optimal counterpulsation frequency was verified by analyzing the hemodynamic effects of different frequency modes of counterpulsation cycles and full cycles.

RESULTS

In the full cycle, CAF, CBF and ATAWSS of coronary and cerebral arteries were the highest when one counterpulsation per cardiac cycle was applied. However, in the counterpulsation cycle, the global and local hemodynamic indicators of coronary and cerebral artery reached the highest when one counterpulsation in one cardiac cycle or two cardiac cycles was applied.

CONCLUSIONS

For clinical application, the results of global hemodynamic indicators in the full cycle have more clinical practical significance. Combined with the comprehensive analysis of local hemodynamic indicators, it can be concluded that for coronary heart disease and cerebral ischemic stroke, applying one counterpulsation per cardiac cycle may provide the optimal benefit.

Model-based evaluation of local hemodynamic effects of enhanced external counterpulsation

BACKGROUND AND OBJECTIVES

The treatment benefits of enhanced external counterpulsation (EECP) heavily depends on hemodynamics. Global hemodynamics of EECP can cause blood flow redistribution in the circulatory system whereas local hemodynamic effects act on vascular endothelial cells (VECs). Local hemodynamic effects of EECP on VECs are important in the treatment of atherosclerosis, but currently cannot be not evaluated. Herein we aim to establish evaluation models of local hemodynamic effects based on the global hemodynamic indicators.

METHODS

We established 0D/3D geometric multi-scale hemodynamic models of the coronary and cerebral artery of two healthy individuals to calculate the global hemodynamic indicators and the local hemodynamic effects. Clinical EECP trials were performed to verify the accuracy of the multi-scale hemodynamic model. The global hemodynamic indicators included diastolic blood pressure/systolic blood pressure (Q = D/S), mean arterial pressure (MAP), internal carotid artery flow (ICAF) and cerebral blood flow (CBF), whereas local hemodynamic effects focused on time-averaged wall shear stress (TAWSS). The correlation between these indicators was analyzed via Pearson correlation coefficient. Significantly related indicators were selected for curve-fitting to establish evaluation models of the coronary and cerebral artery. Moreover, clinical data of a coronary heart disease patient and a cerebral ischemic stroke patient were collected to verify the effectiveness of the application of the established evaluation models to real patients.

RESULTS

For coronary artery, TAWSS was correlated to Q = D/S and ICAF (P < 0.05), whereas for cerebral artery, TAWSS was correlated to MAP and CBF (P < 0.05). The mean square error (MSE) between the evaluated values using evaluation model and the calculated values using 0D/3D model of TAWSS of the coronary and cerebral artery were 5.4% and 1.0%, respectively. The MSE of evaluation model applied to real patients was greater than that applied to healthy individuals, but within an acceptable range.

CONCLUSIONS

The presented error demonstrated validity and accuracy of the evaluation models in clinical patients. Based on the evaluation models, global hemodynamic indicators could be used to evaluate the local hemodynamic effects under the current counterpulsation mode. With TAWSS range of 4-7 Pa as the target range, EECP strategies can further be optimized.

Enhanced external counterpulsation: A new method to alleviate contrast-induced acute kidney injury

BACKGROUND

Contrast-induced acute kidney injury (CI-AKI) is a common complication after exposure to contrast media. Renal ischaemia occurs in the initial stage of CI-AKI, however, there are very few effective measures to improve renal perfusion.

METHODS

A total of 114 patients with an estimated glomerular filtration rate (eGFR) of 60-89 ml/min/1.73m² were randomly assigned to two groups: enhanced external counterpulsation (EECP) group (N = 57) and control group (N = 57). Two hours after contrast exposure, EECP group received EECP treatment for 1 h while no intervention was performed control group. The primary outcome was the incidence of serum cystatin C concentration to 10% above the baseline concentration at 24 h after contrast administration. The secondary outcomes were the incidence of CI-AKI (defined as an increase in serum creatinine concentration to ≥0.5 mg/dl or by 25% compare to the baseline after contrast exposure), contrast clearance and adverse clinical events.

RESULTS

The primary outcome was observed in 26 patients (6 EECP and 20 control; 11% vs. 35%; P = 0.002). CI-AKI occurred in four patients (0 EECP and 4 control; 0% vs. 7%; P = 0.042). The clearance rate of iopromide in the initial 3 h was significantly different between EECP and control group (59.92 ± 8.84 vs 46.80 ± 9.26 ml/min/1.73 m²; P < 0.001). No adverse clinical events were observed in this study.

CONCLUSIONS

This study demonstrates that EECP increases the contrast clearance and may have an effect in reducing the risk of CI-AKI. The study has been registered in Chinese Clinical Trial Registry (ChiCTR 2,000,039,190).

Numerical analysis of hemodynamic effect under different enhanced external counterpulsation (EECP) frequency for cerebrovascular disease: a simulation study

Based on the changes in phase characteristics of blood flow and pressure, enhanced external counterpulsation (EECP) reduces cardiac load and improves cerebral perfusion in patients with cerebrovascular diseases. However, increased cerebral blood flow (CBF) is associated with the rise in blood pressure and its complications. Increased EECP frequency is a valuable solution when combined with the electrical equivalent impedance characteristics of the lumped parameter model (LPM) of the human blood circulation system. Herein, to investigate the effect of different EECP frequencies on CBF perfusion, an LPM was established with cardiopulmonary circulation and eight systemic blood flow units with cerebral autoregulation module of ischemic stroke patients. Then, using differential equations, we analyzed those parameters through hemodynamic simulations in four EECP modes. With related influencing parameters remaining constant, we adjusted the pressure frequency of EECP and found that when compared to the traditional sequential EECP mode, the relative increase rate of CBF was 16.68%, 18.95%, and 21.21% from 1 to 3 Hz, respectively. This study validates the effect of improving blood prefusion with increasing EECP frequency through numerical analysis.

Cerebral and muscle near-infrared spectroscopy during lower-limb muscle activity - volitional and neuromuscular electrical stimulation

Chronic venous insufficiency (CVI) can lead to blood clotting in the deep veins of the legs, a disease known as deep vein thrombosis. An estimated 40 percent of people in the United States have venous insufficiency that may be ameliorated with neuromuscular electrical stimulation (NMES). Near-infrared spectroscopy (NIRS) is a non-invasive optical imaging method for monitoring hemodynamics. NIRS, being an optical technique has no stimulation artefact, can be combined with NMES for theranostics application. In this study, we combined muscle NIRS (mNIRS) with electromyogram (EMG) of the calf muscles to detect blood volume changes (based on total hemoglobin concentration) in the muscle during volitional tiptoe movements at different frequencies. Also, blood volume changes were measured during NMES (using the geko™ device) at different device settings. In the mNIRS+NMES study, we also measured the cerebral hemodynamics using functional NIRS (fNIRS). The mNIRS was conducted using a frequency domain (FD) method (called FDNIRS) that used a multi-distance method to isolate muscle hemodynamics. FDNIRS-EMG study in ten healthy humans found a statistically significant (p<0.05) effect of the tiptoe frequencies on the EMG magnitude (and power) that increased with tiptoe frequency. Also, the muscle blood volume (standing/rest) decreased (p<0.01) with increasing tiptoe frequency and increasing NMES intensity that was statistically significantly (p<0.05) different between males and females. Moreover, increasing NMES intensity led to a statistically significant (p<0.01) increase in the cerebral blood volume - measured with fNIRS. Therefore, combined mNIRS and fNIRS with NMES can provide a theranostics application for brain+muscle in CVI.

Hemodynamic Responses in Carotid Bifurcation Induced by Enhanced External Counterpulsation Stimulation in Healthy Controls and Patients With Neurological Disorders

Enhanced external counterpulsation is a Food and Drug Administration–approved, non-invasive, assisted circulation therapy for ischemic cardiovascular and cerebrovascular diseases. Previous studies have confirmed that EECP stimulation induces largely different cerebral hemodynamic responses in patients with ischemic stroke and healthy controls. However, the underlying mechanisms remain uncertain. We hypothesize that different blood redistributions at the carotid bifurcation may play a key role. Ten subjects were enrolled in this study, namely, five patients with neurological disorders and five young healthy volunteers as controls. Magnetic resonance angiography (MRA) was performed on the carotid artery. All the subjects received a single session of EECP treatment, with external cuff pressures ranging from 20 to 40 kPa. Vascular ultrasound measurements were taken in the common carotid artery (CCA), external carotid artery (ECA) and internal carotid artery (ICA). Three-dimensional patient-specific numerical models were developed to calculate the WSS-derived hemodynamic factors. The results indicated that EECP increased CCA and ECA blood flow in both groups. The ICA blood flow in the patient group exhibited a mean increase of 6.67% during EECP treatment compared with the pre-EECP condition; a mean decrease of 9.2% was observed in the healthy control group. EECP increased the averaged wall shear stress (AWSS) throughout the carotid bifurcation in the patient group; the ICA AWSS of the healthy group decreased during EECP. In both groups, the oscillatory shear index (OSI) in the ICA increased proportionally with external cuff pressure. In addition, the relative resident time (RRT) was constant or slightly decreased in the CCA and ECA in both groups but increased in the ICA. We suggest that the benefits of EECP to patients with neurological disorders may partly result from blood flow promotion in the ICA and increase in WSS at the carotid bifurcation. In the healthy subjects, the ICA blood flow remained constant during EECP, although the CCA blood flow increased significantly. A relatively low external cuff pressure (20 kPa) is recommended as the optimal treatment pressure for better hemodynamic effects. This study may play an important role in the translation of physiological benefits of EECP treatment in populations with or without neurological disorders.

A Numerical Model for Simulating the Hemodynamic Effects of Enhanced External Counterpulsation on Coronary Arteries

Traditional enhanced external counterpulsation (EECP) used for the clinical treatment of patients with coronary heart disease only assesses diastolic/systolic blood pressure (Q = D/S > 1.2). However, improvement of the hemodynamic environment surrounding vascular endothelial cells of coronary arteries after long-term application of EECP is the basis of the treatment. Currently, the quantitative hemodynamic mechanism is not well understood. In this study, a standard 0D/3D geometric multi-scale model of the coronary artery was established to simulate the hemodynamic effects of different counterpulsation modes on the vascular endothelium. In this model, the neural regulation caused by counterpulsation was thoroughly considered. Two clinical trials were carried out to verify the numerical calculation model. The results demonstrated that the increase in counterpulsation pressure amplitude and pressurization duration increased coronary blood perfusion and wall shear stress (WSS) and reduced the oscillatory shear index (OSI) of the vascular wall. However, the impact of pressurization duration was the predominant factor. The results of the standard model and the two real individual models indicated that a long pressurization duration would cause more hemodynamic risk areas by resulting in excessive WSS, which could not be reflected by the change in the Q value. Therefore, long-term pressurization during each cardiac cycle therapy is not recommended for patients with coronary heart disease and clinical treatment should not just pay attention to the change in the Q value. Additional physiological indicators can be used to evaluate the effects of counterpulsation treatment.

A patient-specific modelling method of blood circulatory system for the numerical simulation of enhanced external counterpulsation

Lumped parameter model (LPM) is a common numerical model for hemodynamic simulation of human's blood circulatory system. The numerical simulation of enhanced external counterpulsation (EECP) is a typical biomechanical simulation process based on the LPM of blood circulatory system. In order to simulate patient-specific hemodynamic effects of EECP and develop best treatment strategy for each individual, this study developed an optimization algorithm to individualize LPM elements. Physiological data from 30 volunteers including approximate aortic pressure, cardiac output, ankle pressure and carotid artery flow were clinically collected as optimization objectives. A closed-loop LPM was established for the simulation of blood circulatory system. Aiming at clinical data, a sensitivity analysis for each element was conducted to identify the significant ones. We improved the traditional simulated annealing algorithm to iteratively optimize the sensitive elements. To verify the accuracy of the patient-specific model, 30 samples of simulated data were compared with clinical measurements. In addition, an EECP experiment was conducted on a volunteer to verify the applicability of the optimized model for the simulation of EECP. For these 30 samples, the optimization results show a slight difference between clinical data and simulated data. The average relative root mean square error is lower than 5%. For the subject of EECP experiment, the relative error of hemodynamic responses during EECP is lower than 10%. This slight error demonstrated a good state of optimization. The optimized modeling algorithm can effectively individualize the LPM for blood circulatory system, which is significant to the numerical simulation of patient-specific hemodynamics.

Hemodynamic effects of enhanced external counterpulsation on cerebral arteries: a multiscale study

Background

Enhanced external counterpulsation (EECP) is an effective method for treating patients with cerebral ischemic stroke, while hemodynamics is the major contributing factor in the treatment of EECP. Different counterpulsation modes have the potential to lead to different acute and long-term hemodynamic changes, resulting in different treatment effects. However, various questions about appropriate counterpulsation modes for optimizing hemodynamic effects remain unanswered in clinical treatment.

Methods

A zero-dimensional/three-dimensional (0D/3D) geometric multiscale model of the cerebral artery was established to obtain acute hemodynamic indicators, including mean arterial pressure (MAP) and cerebral blood flow (CBF), as well as localized hemodynamic details for the cerebral artery, which includes wall shear stress (WSS) and oscillatory shear index (OSI). Counterpulsation was achieved by applying pressure on calf, thigh and buttock modules in the 0D model. Different counterpulsation modes including various pressure amplitudes and pressurization durations were applied to investigate hemodynamic responses, which impact acute and long-term treatment effects. Both vascular collapse and cerebral autoregulation were considered during counterpulsation.

Results

Variations of pressure amplitude and pressurization duration have different impacts on hemodynamic effects during EECP treatment. There were small differences in the hemodynamics when similar or different pressure amplitudes were applied to calves, thighs and buttocks. When increasing pressure amplitude was applied to the three body parts, MAP and CBF improved slightly. When pressure amplitude exceeded 200 mmHg, hemodynamic indicators almost never changed, demonstrating consistency with clinical data. However, hemodynamic indicators improved significantly with increasing pressurization duration. For pressurization durations of 0.5, 0.6 and 0.7 s, percentage increases for MAP during counterpulsation were 1.5%, 23.5% and 39.0%, for CBF were 1.2%, 23.4% and 41.6% and for time-averaged WSS were 0.2%, 43.5% and 85.0%, respectively.

Conclusions

When EECP was applied to patients with cerebral ischemic stroke, pressure amplitude applied to the three parts may remain the same. Patients may not gain much more benefit from EECP treatment by excessively increasing pressure amplitude above 200 mmHg. However, during clinical procedures, pressurization duration could be increased to 0.7 s during the cardiac circle to optimize the hemodynamics for possible superior treatment outcomes.

Feasibility and Safety of Using External Counterpulsation to Augment Cerebral Blood Flow in Acute Ischemic Stroke-The Counterpulsation to Upgrade Forward Flow in Stroke (CUFFS) Trial

BACKGROUND

External counterpulsation (ECP) increases perfusion to a variety of organs and may be helpful for acute stroke.

METHODS

We conducted a single-blinded, prospective, randomized controlled feasibility and safety trial of ECP for acute middle cerebral artery (MCA) ischemic stroke. Twenty-three patients presenting within 48 hours of symptom onset were randomized into one of two groups. One group was treated with ECP for 1 hour at a pressure of up to 300 mmHg ("full pressure"). During the procedure, we also determined the highest possible pressure that would augment MCA mean flow velocity (MFV) by 15%. The other group was treated with ECP at 75 mmHg ("sham pressure"). Transcranial Doppler MCA flow velocities and National Institutes of Health Stroke Scale (NIHSS) scores of both groups were checked before, during, and after ECP. Outcomes were assessed at 30 days after randomization.

RESULTS

Although the procedures were feasible to implement, there was a frequent inability to augment MFV by 15% despite maximal pressures in full-pressure patients. In sham-pressure patients, however, MFV frequently increased as shown by increases in peak systolic velocity and end diastolic velocity. In both groups, starting ECP was often associated with contemporaneous improvements in NIHSS stroke scores. There were no between-group differences in NIHSS, modified Rankin Scale Scores, and Barthel Indices, and no device or treatment-related serious adverse events, deaths, intracerebral hemorrhages, or episodes of acute neuro-worsening.

CONCLUSIONS

ECP was safe and feasible to use in patients with acute ischemic stroke. It was associated with unexpected effects on flow velocity, and contemporaneous improvements in NIHSS score regardless of pressure used, with a possibility that even very low ECP pressures had an effect. Further study is warranted.

[The enhanced external counterpulsation as a method of non-invasive auxiliary blood circulation used for the combined rehabilitative treatment of the patients surviving after ischemic stroke (a review)]

The present review of the foreign and domestic literature is concerned with the application of the method of enhanced external counterpulsation (EECP) therapy for the treatment of the patients presenting with various diseases. It is shown that many recent publications report extensive investigations of the clinical and neurophysiological aspects of the application of this method for the combined regenerative treatment of the patients surviving after ischemic stroke (IS). The possibility of the influence of EECP therapy on the system of regulation of the cerebral blood flow, the formation of collateral circulation in the ischemic tissue, and the cellular-humoral mechanisms are considered. It is concluded that the introduction of enhanced external counterpulsation therapy into the program of the combined rehabilitative treatment on an individual basis for the patients surviving after ischemic stroke is pathogenetically substantiated as promoting regression of clinical, neurological, and neuropsychological disorders.

Guidelines for the early management of patients with acute ischemic stroke: a guideline for healthcare professionals from the American Heart Association/American Stroke Association

BACKGROUND AND PURPOSE

The authors present an overview of the current evidence and management recommendations for evaluation and treatment of adults with acute ischemic stroke. The intended audiences are prehospital care providers, physicians, allied health professionals, and hospital administrators responsible for the care of acute ischemic stroke patients within the first 48 hours from stroke onset. These guidelines supersede the prior 2007 guidelines and 2009 updates.

METHODS

Members of the writing committee were appointed by the American Stroke Association Stroke Council's Scientific Statement Oversight Committee, representing various areas of medical expertise. Strict adherence to the American Heart Association conflict of interest policy was maintained throughout the consensus process. Panel members were assigned topics relevant to their areas of expertise, reviewed the stroke literature with emphasis on publications since the prior guidelines, and drafted recommendations in accordance with the American Heart Association Stroke Council's Level of Evidence grading algorithm.

RESULTS

The goal of these guidelines is to limit the morbidity and mortality associated with stroke. The guidelines support the overarching concept of stroke systems of care and detail aspects of stroke care from patient recognition; emergency medical services activation, transport, and triage; through the initial hours in the emergency department and stroke unit. The guideline discusses early stroke evaluation and general medical care, as well as ischemic stroke, specific interventions such as reperfusion strategies, and general physiological optimization for cerebral resuscitation.

CONCLUSIONS

Because many of the recommendations are based on limited data, additional research on treatment of acute ischemic stroke remains urgently needed.

External counterpulsation for acute ischaemic stroke

BACKGROUND

External counterpulsation (ECP) may improve cerebral blood flow, and it has been proposed as a potential therapy for patients with ischaemic stroke.

OBJECTIVES

To assess the efficacy and safety of ECP for acute ischaemic stroke.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register (June 2011), Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, 2011 Issue 2), MEDLINE (1948 to June 2011), EMBASE (1980 to June 2011), CINAHL (1982 to June 2011), AMED (Allied and Complementary Medicine) (1985 to June 2011), China Biological Medicine Database (CBM) (1978 to June 2011), Chinese National Knowledge Infrastructure (CNKI) (1979 to June 2011), Chinese Science and Technique Journals Database (VIP) (1989 to June 2011) and Wanfang Data (1984 to June 2011). We also searched ongoing trials registers, reference lists and relevant conference proceedings and contacted authors and manufacturers of external counterpulsation devices.

SELECTION CRITERIA

Randomised controlled trials (RCTs) in which ECP (started within seven days of stroke onset) was compared with sham treatment or no treatment, or ECP plus routine treatment was compared with routine treatment alone, in patients with acute ischaemic stroke.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data, checked for adverse events data and contacted trialists for missing information.

MAIN RESULTS

We included two trials involving 160 patients. Numbers of death or dependent patients at the end of at least three months follow-up were not reported in either of the included trials. The outcome measure used in the included trials was only the number of participants with improvement of neurological impairment after treatment according to the Modified Edinburgh-Scandinavian Stroke Scale (MESSS) or self-making criteria. ECP was associated with a significant increase in the number of participants whose neurological impairment improved (risk ratio (RR) 1.75, 95% confidence interval (CI) 1.37 to 2.23). Only one trial reported no adverse events.

AUTHORS' CONCLUSIONS

The methodological quality of the included studies was poor, and reliable conclusions could not be drawn from the present data. High-quality and large-scale RCTs are needed.

Hyperacute ischemic stroke management: reperfusion and evolving therapies

Management of acute ischemic stroke patients is organized around several priorities aimed at ensuring optimal patient outcomes, the first of which is reperfusion therapy, followed by determination of pathogenic mechanism by provision of a comprehensive workup to determine probable cause of the ischemic stroke or transient ischemic attack, for the purpose of providing appropriate prophylaxis for subsequent events. Provision of secondary prevention measures along with therapies that prevent complications associated with neurologic disability, and evaluation for the most appropriate level of rehabilitation services are the final priorities during acute hospitalization. This article provides an overview of reperfusion therapies and emerging hemodynamic treatments for hyperacute ischemic strokes. Gaps in the scientific evidence that are driving current blood flow augmentation research are identified.

Perfusion Augmentation in Acute Stroke Using Mechanical Counter-Pulsation–Phase IIa

Background and Purpose— External counterpulsation (ECP) improves coronary perfusion, increases left ventricular stroke volume similar to intraaortic balloon counterpulsation, and recruits arterial collaterals within ischemic territories. We sought to determine ECPs effect on middle cerebral artery (MCA) blood flow augmentation in normal controls as a first step to support future clinical trials in acute stroke.

Methods— Healthy volunteers were recruited and screened for exclusions. Bilateral 2-MHz pulsed wave transcranial Doppler (TCD) probes were mounted by head frame, and baseline M1 MCA TCD measurements were obtained. ECP was then initiated using standard procedures for 30 minutes, and TCD readings were repeated at 5 and 20 minutes. Physiological correlates associated with ECP-TCD waveform morphology were identified, and measurable criteria for TCD assessment of ECP arterial mean flow velocity (MFV) augmentation were constructed.

Results— Five subjects were enrolled in the study. Preprocedural M1 MCA TCD measurements were within normal limits. Onset of ECP counterpulsation produced an immediate change in TCD waveform configuration with the appearance of a second upstroke at the dicrotic notch, labeled peak diastolic augmented velocity (PDAV). Although end-diastolic velocities did not increase, both R-MCA and L-MCA PDAVs were significantly higher than baseline end-diastolic values ( P <0.05 Wilcoxon rank-sum test) at 5 and 20 minutes. Augmented MFVs (aMFVs) were also significantly higher than baseline MFV in the R-MCA and L-MCA at both 5 and 20 minutes ( P <0.05).

Conclusions— ECP induces marked changes in cerebral arterial waveforms and augmented peak diastolic and mean MCA flow velocities on TCD in 5 healthy subjects.

Preliminary Findings of External Counterpulsation for Ischemic Stroke Patient With Large Artery Occlusive Disease

Background and Purpose— We aimed to investigate the feasibility and therapeutic effect of external counterpulsation (ECP) in ischemic stroke.

Methods— The trial was a randomized, crossover, assessment-blinded, proof-of-concept trial. ECP treatment consisted of 35 daily 1-hour sessions. Patients were randomized to either early (ECP weeks 1 to 7 and no ECP weeks 8 to 14) or late group (no ECP weeks 1 to 7 and ECP weeks 8 to 14). Primary outcomes were an overall change in National Institutes of Health Stroke Scale (NIHSS) and cerebral blood flow estimated by color velocity imaging quantification. Secondary outcomes were change in NIHSS, color velocity imaging quantification, favorable functional outcome (modified Rankin scale, 0 to 2), and stroke recurrence at weeks 7 and 14, respectively.

Results— Fifty patients were recruited. At week 7, there was a significant change in NIHSS (early 3.5 vs late 1.9; P =0.042). After adjusting for treatment sequence, ECP was associated with a favorable trend of change in NIHSS of 2.1 vs 1.3 for non-ECP ( P =0.061). Changes of color velocity imaging quantification were not significant but tended to increase with ECP. At week 14, a favorable functional outcome was found in 100% of early group patients compared to 76% in the late group ( P =0.022).

Conclusion— ECP is feasible for ischemic stroke patients with larger artery disease.

Mechanisms and evidence for the role of enhanced external counterpulsation in heart failure management

Balloon counterpulsation has gained widespread acceptance as a therapy for cardiogenic shock. However, over the past four decades a parallel method of noninvasive counterpulsation, enhanced external counterpulsation (EECP), has been defined and developed. Mechanisms of benefit for this technology continue to emerge and include enhanced coronary and other key target organ perfusion beds. Other mechanisms include angiogenesis and enhanced cellular metabolism. Beyond putative mechanisms there is ample evidence for improved and sustained outcomes in patients with and without left ventricular dysfunction. This evidence comes from long-term registry reports and randomized clinical trials. With respect to heart failure (HF), there is registry, pilot trial, and randomized clinical trial evidence of safety and efficacy. This paper summarizes some of the mechanisms and outcomes of EECP in HF patients and helps to elucidate the role of EECP in the management of patients with chronic HF.

Enhanced external counterpulsation: a new technique to augment renal function in liver cirrhosis

BACKGROUND

Advanced liver cirrhosis is characterized by cardiovascular changes, such as low arterial blood pressure, peripheral vasodilation and renal vasoconstriction. As a consequence, renal hypoperfusion, impaired diuresis and natriuresis and eventual hepatorenal syndrome may ensue. Previous studies using head-out water immersion to increase central blood volume have demonstrated the functional nature of the renal abnormalities. Enhanced external counterpulsation (EECP) is a new non-invasive cardiac assist device to augment diastolic blood pressure by electrocardiogram-triggered diastolic inflation and deflation of cuffs wrapped around the lower extremities. We investigated whether EECP would improve renal dysfunction of liver cirrhosis.

METHODS

Twelve healthy controls and 19 patients with liver cirrhosis were observed during 2 h of baseline followed by 2 h of EECP. The following parameters of renal and cardiovascular function were measured: renal plasma flow by para-aminohippurate clearance, glomerular filtration rate (GFR) by inulin clearance, urine flow rate, urinary excretion rates of sodium and chloride, mean arterial blood pressure (MAP), renal vascular resistance (RVR) and plasma concentrations of renin, atrial natriuretic peptide (ANP), endothelin-1, antidiuretic hormone, epinephrine and N-epinephrine.

RESULTS

EECP was well tolerated by healthy controls and cirrhotic patients alike. EECP increased MAP (cirrhotic patients: from 74+/-18 to 88+/-20 mmHg, P<0.01; controls: from 89+/-8 to 94+/-5 mmHg, P = NS) and ANP (cirrhotic patients: from 23+/-18 to 30+/-20 ng/l, P<0.05; controls: from 11+/-4 to 16+/-5 ng/l, P<0.01). The plasma renin concentration decreased (cirrhotic patients: from 98+/-98 to 58+/-57 ng/l, P<0.01; controls: from 4.6+/-1.6 to 3.4+/-1.1 ng/l, P<0.01). This was associated with improvement of the urinary flow rate (cirrhotic patients: from 3.6+/-1.8 to 4.6+/-0.7 ml/min, P<0.05; controls: from 1.8+/-1.5 to 2.8+/-1.9 ml/min, P<0.05), as well as of the sodium and chloride excretion rates in both groups. However, in contrast to healthy controls, GFR and renal plasma flow in cirrhotic patients failed to rise significantly. Renal vascular resistance fell numerically in healthy controls (68+/-5 vs 55+/-4 mmHg . min/l; P = NS). In contrast, RVR showed a significant increase by approximately 20% in cirrhosis (67+/-4 vs 80+/-8 mmHg . min/l; P<0.05). Endothelin-1 levels fell in controls (0.38+/-0.42 vs 0.31+/-0.35; P<0.05), whereas they remained statistically unchanged in cirrhotic patients. Epinephrine, N-epinephrine and vasopressin were not altered by EECP in either group.

CONCLUSIONS

EECP is an effective procedure to augment renal excretory function in healthy volunteers as well as in patients with cirrhosis. In healthy volunteers, GFR and renal plasma flow increased during EECP. In contrast, these parameters remained unchanged in the patients and their renal vascular resistance increased during EECP. Therefore, EECP improves diuresis, but does not influence the vasoconstrictive dysregulation of the kidneys in liver cirrhosis.

Enhanced external counterpulsation does not compromise cerebral autoregulation

OBJECTIVES

Enhanced external counterpulsation (EECP) rhythmically augments blood pressure (BP) by diastolic lower-body compression. Recently, we showed decreased mean cerebral blood flow velocity (CBFVmean) in young healthy persons during EECP, but unchanged CBFVmean in atherosclerotic patients. In this study, we assessed EECP effects on dynamic cerebral autoregulation (CA).

MATERIAL & METHODS

In 23 healthy persons and 15 atherosclerotic patients we monitored heart rate (HR), mean BP (BPmean) and CBFVmean before and during 5 min EECP. We analyzed spectral powers of HR, BPmean and CBFVmean in the low (LF: 0.04-0.15 Hz) and high (HF: 0.15-0.5 Hz) frequency ranges to determine CA from the LF-transfer function gain and phase shift between BPmean and CBFVmean oscillations.

RESULTS

EECP increased HR and BPmean, while transfer function gain and phase shift remained stable.

CONCLUSIONS

Stable gain and phase values suggest that EECP does not compromise CA and, therefore, does not seem to bear cerebrovascular risks.

ACCELERATED REPERFUSION OF POORLY PERFUSED RETINAL AREAS IN CENTRAL RETINAL ARTERY OCCLUSION AND BRANCH RETINAL ARTERY OCCLUSION AFTER A SHORT TREATMENT WITH ENHANCED EXTERNAL COUNTERPULSATION

BACKGROUND

To date, no satisfactory therapy has become available for patients with acute central retinal artery occlusion (CRAO) or branch retinal artery occlusion (BRAO). Enhanced external counterpulsation (EECP) is a new noninvasive procedure that increases perfusion of inner organs. In the current study, the authors measured the impact of EECP on reperfusion in ischemic retinal tissue.

METHODS

In a prospective, randomized study, 20 patients with CRAO or BRAO were included. Ten patients were given hemodilution therapy and 2 hours of EECP, and 10 patients were given regular hemodilution therapy only. Quantification of changes in retinal perfusion was carried out by means of scanning laser Doppler flowmetry (in arbitrary units).

RESULTS

Enhanced external counterpulsation caused no observable adverse events. A significant increase in perfusion occurred immediately after EECP in the ischemic retinal areas (57 +/- 19 arbitrary units versus 99 +/- 14 arbitrary units). In contrast, no change was measured in the group not treated with EECP (83 +/- 19 arbitrary units versus 89 +/- 44 arbitrary units). Forty-eight hours later, a significant increase in perfusion could be shown in the ischemic retina of both groups, and no significant difference of perfusion was found between the two groups any longer.

CONCLUSION

The current study suggests that EECP could be a clinically useful and safe procedure in patients with CRAO or BRAO to accelerate recovery of perfusion in ischemic retinal areas.

Enhanced external counterpulsation improves skin oxygenation and perfusion

BACKGROUND

Enhanced external counterpulsation (EECP) augments diastolic and reduces systolic blood pressures. Enhanced external counterpulsation has been shown to improve blood flow in various organ systems. Beneficial effects on skin perfusion might allow EECP to be used in patients with skin malperfusion problems. This study was performed to assess acute effects of EECP on superficial skin blood flow, transdermal oxygen and carbon dioxide pressures.

MATERIALS AND METHODS

We monitored heart rate, blood pressure, transdermal blood flow as well as oxygen and carbon dioxide pressures in 23 young, healthy persons (28 +/- 4 years) and 15 older patients (64 +/- 7 years) with coronary artery disease before, during and 3 min after 5 min EECP. Friedman test was used to compare the results of 90-s epochs before, during and after EECP. Significance was set at P < 0.05.

RESULTS

Enhanced external counterpulsation increased heart rate and mean blood pressure. During EECP, transdermal oxygen pressure and concentration of moving blood cells increased while transdermal carbon dioxide pressure and velocity of moving blood cells decreased significantly in both groups. After EECP, transdermal carbon dioxide pressure was still reduced while the other parameters returned to baseline values.

CONCLUSIONS

Improved skin oxygenation and carbon dioxide clearance during EECP seem to result from the increased concentration and reduced flow velocity, i.e. prolonged contact time, of erythrocytes. The increased concentration of moving blood cells and the decreased velocity of moving blood cells at both tested skin sites indicate peripheral vasodilatation.

Changes of cerebral blood flow velocities during enhanced external counterpulsation

OBJECTIVES

Intra-aortic counterpulsation is the most frequently used cardiac assist device. However, there are only few studies of the effects of counterpulsation on cerebral blood flow and these report conflicting outcomes. The new enhanced external counterpulsation (EECP) technique reproduces non-invasively the effects of intra-aortic counterpulsation. In this study, we evaluated effects of EECP on blood pressure (BP) and on cerebral flow velocity (CBFV).

SUBJECTS AND METHODS

Twenty-three healthy controls and 15 atherosclerotic patients each underwent a 5-min session of EECP. Before, during and after EECP we monitored heart rate, beat-to-beat radial artery BP and CBFV.

RESULTS

EECP induced a second increase in BP and CBFV during diastole with a significant increase of mean BP and a decrease of systolic BP in patients and controls. Mean CBFV increased in both groups during the first 5 s of EECP. After 3 min of EECP, diastolic CBFV was still higher than at baseline, but systolic CBVF was lower than at baseline; mean CBFV was as low as before EECP in the patients and lower than the baseline values in the controls. Three minutes after ending EECP, mean and systolic BP were lower in the patients than the corresponding baseline values. Otherwise, CBFV and BP values did not differ from baseline in patients and controls.

CONCLUSION

Cerebral autoregulation ensures the constancy of cerebral blood flow even though EECP creates marked systemic changes. In the patients, the decrease of BP after EECP with maintained CBFV indicates an improved BPCBFV relation and a more economic autoregulation.

Enhanced external counterpulsation improves endothelial function in patients with symptomatic coronary artery disease

OBJECTIVES

The goal of this study was to examine the effect of enhanced external counterpulsation (EECP) on endothelial function.

BACKGROUND

Enhanced external counterpulsation improves symptoms and exercise tolerance in patients with symptomatic coronary artery disease (CAD). However, the exact mechanisms by which this technique exerts its clinical benefit are unclear.

METHODS

Reactive hyperemia-peripheral arterial tonometry (RH-PAT), a noninvasive method to assess peripheral endothelial function by measuring reactive hyperemic response in the finger, was performed in 23 patients with refractory angina undergoing a 35-h course of EECP. In each patient RH-PAT measurements were performed before and after the first, at midcourse, and the last EECP session. In addition, RH-PAT response was assessed one month after completion of EECP therapy; RH-PAT index, a measure of reactive hyperemia, was calculated as the ratio of the digital pulse volume during reactive hyperemia divided by that at rest.

RESULTS

Enhanced external counterpulsation led to symptomatic improvement (>/=1 Canadian Cardiovascular Society class) in 17 (74%) patients; EECP was associated with a significant immediate increase in average RH-PAT index after each treatment (p < 0.05). In addition, average RH-PAT index at one-month follow-up was significantly higher than that before EECP therapy (p < 0.05). When patients were divided by their clinical response, RH-PAT index at one-month follow-up increased only in those patients who experienced clinical benefit.

CONCLUSIONS

Enhanced external counterpulsation enhances peripheral endothelial function with beneficial effects persisting at one-month follow-up in patients with a positive clinical response. This suggests that improvement in endothelial function may contribute to the clinical benefit of EECP in patients with symptomatic CAD.

Pneumatic external counterpulsation: a new noninvasive method to improve organ perfusion

Pneumatic external counterpulsation, which is operated by applying electrocardiographic-triggered diastolic pressure via air-filled cuffs to the vascular limbs of lower limbs, is a relatively new therapeutic option for patients with angina pectoris and cerebrovascular diseases like transient ischemic attacks or sudden deafness. In this study, an augmentation in flow volume in the carotid, renal, and hepatic arteries from 20% to 25% and in the coronary arteries from 20% to 40%, as well as an increase in stroke volume by 12% was demonstrated; this shows the therapeutic results in patients with diseases caused by disturbed organ perfusion.