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Ann Thorac Surg 2001;71:S188-S189
© 2001 The Society of Thoracic Surgeons
a Division of Cardiothoracic Surgery, Department of Surgery, College of Physicians and Surgeons, Columbia University, New York, New York, USA
Address reprint requests to Dr Williams, P&S 17-401, 630 West 168th St, New York, NY 10032
e-mail: mw365{at}columbia.edu
Presented at the Fifth International Conference on Circulatory Support Devices for Severe Cardiac Failure, New York, NY, Sept 15–17, 2000.
Abstract
Epicardial direct cardiac compression for cardiogenic shock avoids a blood surface interface with associated thromboembolic and immunologic sequelae and could be placed rapidly with technical ease. The Cardio Technologies device provides synchronized biventricular cardiac compression, is placed via a thoracotomy, and remains on the heart without need for sutures. In preclinical work, the system has successfully restored cardiac function to near normal in the setting of heart failure. The CardioSupport system offers an attractive and novel alternative for treating cardiogenic shock and is being prepared for upcoming clinical trials.
Epicardial direct cardiac compression (DCC) was first conceived by George Anstadt in 1965 [1]. Unlike Anstadt’s original work, the CardioSupport System is intended for synchronized augmented compression of the failing heart and not primarily as a cardiopulmonary resuscitation (CPR) device. The system avoids a blood-device interface and in theory should result in lower thromboembolic and immunologic complications than those induced by blood-contacting devices. Additionally, due to its epicardial location, the device can be placed rapidly through a thoracotomy without the aid of cardiopulmonary bypass. Finally, the device may be placed in a nontraditional setting such as the intensive care unit or emergency room.
Physiology of direct cardiac compression
The direct effect of epicardial compression is to shift the end-systolic pressure-volume relationship (ESPVR) upward by an amount proportional to the pressure applied on the heart by the compression device. The magnitude of the upward shift is approximately 40% of the pressure applied by the device. Because of this, ventricular function must deteriorate by about 30% before a beneficial effect from DCC can be realized [2]. The effect on the end-diastolic pressure-volume relationship (EDPVR) is slight, with a leftward shift [2] that is more prominent in the right ventricle. DCC is able to accomplish all of this without an increase in myocardial oxygen demand [3].
Device description
The Cardio Technologies, Inc (Pine Brook, NJ) CardioSupport System (Fig 1) is intended to be implanted using a thoracotomy. The device is placed from the apex up to the atrioventricular groove and adheres to the heart by means of suction (-200 mm Hg) applied at the apex. An inner suction membrane conforms to the epicardial surface to provide a seal and strengthen the attachment. The innermost membrane also contains two patch electrodes that allow electrocardiogram synchronization of the device with the native cardiac cycle. The electrodes can also be utilized for cardioversion if necessary. The device also contains a rigid outer structural component, a polyurethane inflation bladder, and vacuum and inflation lines.
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Summary of preclinical studies
The device was tested in a canine model of acute heart failure using coronary microembolization. These studies revealed the device was efficacious in augmenting heart failure with resulting increases in cardiac output and mean arterial pressure. The effect was augmented most in animals with more severe heart failure [2].
This technology is most efficacious if combined with preload and afterload manipulations [4]. Because the device does appear to affect the EDPVR, increasing preload resulted in an improvement in device augmentation. Afterload reduction was also found to be beneficial because the neurohormonal milieu of heart failure results in vasoconstriction. If a vasodilating agent was added, especially with further preload augmentation, the device augmentation returned cardiac function to near baseline values. Finally, the device has been implanted in healthy sheep for periods up to 7 days without adverse events; more data are forthcoming (unpublished data).
Future
The intended application for the device will be for short-term support (< 7 days) of any cause of cardiogenic shock, including postcardiotomy failure, myocarditis, and acute myocardial infarction. As these populations will to a great extent determine the number of eligible patients for longer term support, creation of bridging technologies like the DCC will substantially augment the population of patients requiring longer term implantable devices.
References
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