Brief Reports

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

This paper presents the results of research focused on the adaptation of a hybrid simulator of the human circulatory system to the physical reproduction of the haemodynamic conditions prevailing in the apex of the heart. This report describes the principle of operation of the hybrid simulator and presents two methods of its modification. The work includes analysis of the algorithm verification and describes problems that appeared during research. A comparison of the results obtained for both modification methods is shown, as well as preliminary simulation results for a constant-flow ventricle assist device joined to the hybrid simulator operating in the apex of the heart-aorta configuration.

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.

Pneumatic leg sleeves are widely used after prolonged operations for prevention of venous stasis. In healthy volunteers they increase cardiac function. We evaluated the hemodynamic effects and safety of intermittent sequential pneumatic compression (ISPC) leg sleeves in patients with chronic congestive heart failure (CHF).

We studied 19 patients with systolic left ventricular dysfunction and CHF. ISPC leg sleeves, each with 10 air cells, were operated by a computerized compressor, exerting 2 cycles/min. Hemodynamic and echocardiographic parameters were measured before, during, and after ISPC activation. The baseline mean left ventricular ejection fraction was 29 ± 9.2%, median 32%, range 10%–40%. Cardiac output (from 4.26 to 4.83 L/min; P = .008) and stroke volume (from 56.1 to 63.5 mL; P = .029) increased significantly after ISPC activation, without a reciprocal increase in heart rate, and declined after sleeve deactivation. Systemic vascular resistance (SVR) decreased significantly (from 1,520 to 1,216 dyne-s/cm⁵; P = .0005), and remained lower than the baseline level throughout the study. There was no detrimental effect on diastolic function and no adverse clinical events, despite increased pulmonary venous return.

ISPC leg sleeves in patients with chronic CHF do not exacerbate symptoms and transiently improve cardiac output through an increase in stroke volume and a reduction in SVR.

External counterpulsation (ECP) is a noninvasive method used to augment cerebral perfusion but the optimal use of ECP in ischemic stroke has not been well documented. We aimed to investigate the effects of ECP treatment pressure on cerebral blood flow and blood pressure (BP). We recruited 38 ischemic stroke patients with large artery occlusive disease and 20 elderly controls. We commenced ECP treatment pressure at 150 mmHg and gradually increased to 187.5, 225 and 262.5 mmHg. Mean cerebral blood flow velocities (CBFV) of bilateral middle cerebral arteries and continuous beat-to-beat BP were recorded before ECP and during each pressure increment for 3 minutes. Patient CBFV data was analyzed based on whether it was ipsilateral or contralateral to the infarct. Mean BP significantly increased from baseline in both stroke and control groups after ECP commenced. BP increased in both groups following raised ECP pressure and reached maximum at 262.5 mmHg (patients 16.9% increase versus controls 16.52%). The ipsilateral CBFV of patients increased 5.15%, 4.35%, 4.55% and 3.52% from baseline under the four pressures, respectively. All were significantly higher than baseline but did not differ among different ECP pressures; contralateral CBFV changed likewise. Control CBFV did not increase under variable pressures of ECP. ECP did increase CBFV of our patients to a roughly equal degree regardless of ECP pressure. Among the four ECP pressures tested, we recommend 150 mmHg as the optimal treatment pressure for ischemic stroke due to higher risks of hypertension-related complications with higher pressures.

To investigate the therapeutic value of enhanced external counterpulsation (EECP) on recovery of cerebral blood flow following cardiac arrest (CA) and successful resumption of spontaneous circulation (ROSC) by cardiopulmonary resuscitation.

CA models were conducted using beagle dogs induced by alternating current. After successful ROSC by cardiopulmonary resuscitation, 16 dogs were randomly divided into the EECP and control group (n = 8 per group). Dogs underwent dynamic contrast-enhanced and diffusion-weighted magnetic resonance imaging at baseline prior to CA and during the 3 days following ROSC. Mean blood pressure, right common carotid artery blood flow, intracranial microcirculation and blood lactate levels were measured. Neurological outcome was assessed by the neurologic deficit score. Hematoxylin-eosin staining and transmission electron microscopy were performed for morphology and microconstruction of the cerebral cortex.

The EECP group exhibited a significant elevation in right common carotid artery blood flow, intracranial microcirculation and a substantial decrease in blood lactate levels relative to the control group. Relative cerebral blood flow and volume were higher in the EECP group during the 3 days. Apparent diffusion coefficients were significantly higher in the EECP group on the first and third days. After ROSC, the neurologic deficit score was significantly higher in the control group compared to those in the EECP group during the three days of experiment. The cell swelling of neurons and increase of mitochondrial mass were more pronounced in the control group.

EECP is beneficial for recovery of cerebral blood flow and attenuation of ischemic cerebral edema following CA and successful ROSC.

Refractory angina (RFA) is a debilitating disease characterized by cardiac pain resistant to conventional treatments for coronary artery disease including nitrates, calcium-channel and β-adrenoceptor blockade, vasculoprotective agents, percutaneous coronary interventions, and coronary artery bypass grafting. The mortality rate of patients living with RFA is not known but is thought to be in the range of approximately 3%. These individuals suffer severely impaired health-related quality of life with recurrent and sustained pain, poor general health status, psychological distress, impaired role functioning, and activity restriction. Effective care for RFA sufferers in Canada is critically underdeveloped. These guidelines are predicated upon a 2009 Canadian Cardiovascular Society (CCS) Position Statement which identified that underlying the problem of RFA management is the lack of a formalized, coordinated, interprofessional strategy between the cardiovascular and pain science/clinical communities. The guidelines are therefore a joint initiative of the CCS and the Canadian Pain Society (CPS) and make practice recommendations about treatment options for RFA that are based on the best available evidence. Concluding summary recommendations are also made, giving direction to future clinical practice and research on RFA management in Canada.

L'angine de poitrine réfractaire (APR) est une maladie débilitante caractérisée par une douleur cardiaque résistant aux traitements traditionnels de la maladie coronarienne incluant les nitrates, le canal calcique et le blocage des récepteurs β-adrénergiques, les agents vasculoprotecteurs, les interventions coronariennes percutanées et le pontage aortocoronarien. Le taux de mortalité des patients vivant avec une APR n'est pas connu, mais est présumé se situer à environ 3 %. Ces individus souffrent sévèrement de leur qualité de vie liée à leur santé déficiente, dont une douleur récurrente et soutenue, un mauvais état de santé général, une détresse psychologique, un déficit de fonctionnement et une restriction d'activité. Au Canada, l'efficacité des soins offerts aux patients souffrant d'une APR est dramatiquement sous-développée. Ces lignes directrices s'appuient sur un énoncé de position de la Société canadienne de cardiologie (SCC) 2009 qui déterminait que le problème sous-jacent de la gestion de l'APR est le manque de stratégies interprofessionnelles, coordonnées et formalisées, entre les communautés clinique et scientifique dans les domaines cardiovasculaire et de la douleur. Les lignes directrices sont par conséquent une initiative conjointe de la SCC et de la Société canadienne de la douleur (SCD) et font des recommandations pratiques sur les options de traitement de l'APR qui sont basées sur les meilleures preuves disponibles. Des recommandations sont aussi faites, donnant une direction à la pratique clinique future et à la recherche sur la gestion de l'APR au Canada.