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Intraaortic Balloon Pumping
EDITORIALS
Intraaortic Balloon Pumping Watts R. Webb, M.D.
Extensive experience with intraaortic balloon pumping (IABP), which was originally perceived primarily as assistance in acute cardiogenic shock, has demonstrated that it has its greatest value in the perioperative period. Numerous physiological studies have shown that balloon pumping with any of the several commercial devices now available can reduce the workload and oxygen demands of the heart while increasing coronary flow and cardiac output. It arrests the vicious cycle of decreased peripheral flow leading to hypoxic acidosis and progressive myocardial depression. Another beneficial factor more keenly appreciated recently is the reduction of left ventricular enddiastolic pressure. Coronary flow, particularly to the subendocardial area-which is the most vulnerable-depends on the differential between aortic diastolic pressure and left ventricular intracavitary diastolic pressure. Any reduction in the left ventricular diastolic pressure aids in maintaining viability of the entire inner layer of the left ventricle, thus preventing the previously rather frequent episodes of global subendocardia1 hemorrhagic necrosis. Hearts that have been impaired, whether chronically, such as from overdistention, or acutely, from hypoxia, hypothermia, or ischemia, often can have this trend reversed with a period of assistance. More and more experience is accumulating to demonstrate that IABP should be used as soon as postinfarction or postoperative cardiac failure is discerned rather than after protracted attempts at balancing intravascular volumes and inotropic or vasoactive agents. These latter have now been well documented to increase myocardial ischemia and even extend the ultimate area of myocardial infarct. The support of patients in a low cardiac output state has proved to be of great value, not only in Address reprint requests to Dr. Webb, Department of Surgery, State University of New York Upstate Medical Center, 750 E Adams St, Syracuse, NY 13210.
571
patients suffering cardiogenic shock but also in those with pump failure from acute mechanical defects secondary to myocardial infarction, such as aneurysm, mitral regurgitation, or ventricular septa1 defect. It has had more limited but very effective use in the preoperative support of patients with preinfarction angina or severe obstructive lesions of the left main coronary artery. Patients with ischemic arrhythmias often can be stabilized. In all these situations the patient usually can be sustained and stabilized during cardiac catheterization, which can then be followed by an appropriate operation. It is overwhelmingly evident that innumerable patients who otherwise would have died without ever coming to operation are now reaching the surgeon. The salvage rates, though not high, are impressive in view of the extensive disease present. The use of IABP in cardiogenic shock has brought forcibly to our attention another important fact: cardiogenic shock from pump failure does not occur until some 40 to 50% of the myocardium has been rendered nonfunctional. This usually means multiple-vessel disease and multiple infarctions rather than a first infarction from single-vessel disease. While the patient may die of a fatal arrhythmia from a very small infarction, pump failure usually means that there is inadequate viable myocardium for continued long-term function. Thus, early IABP support and operation are much more effective in patients who have mechanical complications of coronary arterial disease than in those with extensive myocardial damage alone. IABP has now proved itself to be effective and extremely safe with a very low incidence of complications, and these usually minor. Longterm assistance can easily be managed by the well-trained nursing personnel in an intensive care unit. While in most instances IABP is required for only a few hours or days, it can be safely and effectively used for weeks; our patient with the longest survival following IABP had assistance for 22 days.
572 The Annals of Thoracic Surgery Vol 21 No 6 June 1976
While the problem of femoral artery cannulation is relatively slight, it is hoped that an equally effective, totally noninvasive apparatus will become available. Present external counterpulsation devices have proved somewhat less effective and are extremely uncomfortable to the patient, so that only rarely can they be used for longer than an hour or two at any one time. With the demonstration that counterpulsation can re-
duce the size of an infarct following coronary occlusion, it becomes important that better, safer, and more usable apparatus and methods for noninvasive counterpulsation be developed. In view of its present safety, effectiveness, and extreme value, intraaortic balloon assistance appears to be a very desirable, if not absolutely essential part of the armamentarium of every cardiac surgical team.
Intraaortic Balloon Pumping Watts R. Webb, M.D.
Extensive experience with intraaortic balloon pumping (IABP), which was originally perceived primarily as assistance in acute cardiogenic shock, has demonstrated that it has its greatest value in the perioperative period. Numerous physiological studies have shown that balloon pumping with any of the several commercial devices now available can reduce the workload and oxygen demands of the heart while increasing coronary flow and cardiac output. It arrests the vicious cycle of decreased peripheral flow leading to hypoxic acidosis and progressive myocardial depression. Another beneficial factor more keenly appreciated recently is the reduction of left ventricular enddiastolic pressure. Coronary flow, particularly to the subendocardial area-which is the most vulnerable-depends on the differential between aortic diastolic pressure and left ventricular intracavitary diastolic pressure. Any reduction in the left ventricular diastolic pressure aids in maintaining viability of the entire inner layer of the left ventricle, thus preventing the previously rather frequent episodes of global subendocardia1 hemorrhagic necrosis. Hearts that have been impaired, whether chronically, such as from overdistention, or acutely, from hypoxia, hypothermia, or ischemia, often can have this trend reversed with a period of assistance. More and more experience is accumulating to demonstrate that IABP should be used as soon as postinfarction or postoperative cardiac failure is discerned rather than after protracted attempts at balancing intravascular volumes and inotropic or vasoactive agents. These latter have now been well documented to increase myocardial ischemia and even extend the ultimate area of myocardial infarct. The support of patients in a low cardiac output state has proved to be of great value, not only in Address reprint requests to Dr. Webb, Department of Surgery, State University of New York Upstate Medical Center, 750 E Adams St, Syracuse, NY 13210.
571
patients suffering cardiogenic shock but also in those with pump failure from acute mechanical defects secondary to myocardial infarction, such as aneurysm, mitral regurgitation, or ventricular septa1 defect. It has had more limited but very effective use in the preoperative support of patients with preinfarction angina or severe obstructive lesions of the left main coronary artery. Patients with ischemic arrhythmias often can be stabilized. In all these situations the patient usually can be sustained and stabilized during cardiac catheterization, which can then be followed by an appropriate operation. It is overwhelmingly evident that innumerable patients who otherwise would have died without ever coming to operation are now reaching the surgeon. The salvage rates, though not high, are impressive in view of the extensive disease present. The use of IABP in cardiogenic shock has brought forcibly to our attention another important fact: cardiogenic shock from pump failure does not occur until some 40 to 50% of the myocardium has been rendered nonfunctional. This usually means multiple-vessel disease and multiple infarctions rather than a first infarction from single-vessel disease. While the patient may die of a fatal arrhythmia from a very small infarction, pump failure usually means that there is inadequate viable myocardium for continued long-term function. Thus, early IABP support and operation are much more effective in patients who have mechanical complications of coronary arterial disease than in those with extensive myocardial damage alone. IABP has now proved itself to be effective and extremely safe with a very low incidence of complications, and these usually minor. Longterm assistance can easily be managed by the well-trained nursing personnel in an intensive care unit. While in most instances IABP is required for only a few hours or days, it can be safely and effectively used for weeks; our patient with the longest survival following IABP had assistance for 22 days.
572 The Annals of Thoracic Surgery Vol 21 No 6 June 1976
While the problem of femoral artery cannulation is relatively slight, it is hoped that an equally effective, totally noninvasive apparatus will become available. Present external counterpulsation devices have proved somewhat less effective and are extremely uncomfortable to the patient, so that only rarely can they be used for longer than an hour or two at any one time. With the demonstration that counterpulsation can re-
duce the size of an infarct following coronary occlusion, it becomes important that better, safer, and more usable apparatus and methods for noninvasive counterpulsation be developed. In view of its present safety, effectiveness, and extreme value, intraaortic balloon assistance appears to be a very desirable, if not absolutely essential part of the armamentarium of every cardiac surgical team.