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A Prospective Evaluation of the Pulsatile Assist Device
A Prospective Evaluation of the Pulsatile Assist Device G. Lionel Zumbro, Jr., M.D., George Shearer, C.C.P., Malcolm E. Fishback, M.D., a n d Ronald F. Galloway, M.D.
Presented at the Fifteenth Annual Meeting of The Society of Thoracic Surgeons, Jan 15-17, 1979, Phoenix, AZ.
Materials and Methods From October, 1977, to May, 1978, 100 consecutive patients undergoing coronary artery bypass operation were randomized prospectively. Fifty patients received nonpulsatile perfusion and 50 received pulsatile perfusion produced by the PAD.* All operations were performed by the same primary surgeon ( G . L. Z .) utilizing intermittent ischemic arrest and moderate systemic hypothermia (28" to 30°C). The PAD was turned off while the aorta was clamped to avoid intimal injury. Saphenous veins were utilized almost exclusively. Only 6 patients received an internal mammary graft. All distal anastomoses were performed first with the patient on cardiopulmonary bypass, and proximal anastomoses were performed last while the patient was being rewarmed. Perioperative myocardial injury was evaluated by serial electrocardiograms and creatine phosphokinase (CPK) I1 isoenzyme studies performed immediately after operation and for the first three postoperative days. Myocardial scans with technetium 99m-labeled pyrophosphate were done between the second and fourth postoperative days. Patients were considered to have sustained a perioperative myocardial infarction if the ECG demonstrated new Q waves, loss of R wave progression or permanent conduction defects. Patients with positive myocardial scans were considered to have sustained a perioperative myocardial infarction regardless of ECG findings. Lesser degrees of myocardial injury were evaluated by S-T segment depression of 2 mm or more and CPK I1 isoenzyme levels. Blood trauma was evaluated by measuring free plasma hemoglobin and platelet counts immediately following operation. Data were analyzed by the Student t test, standard chi-square test, or fixed effects analy-
Address reprint requests to Dr. Zumbro, Suite 2-D, 820 St. Sebastian Way, Augusta, GA 30902.
"Datascope Corp., Paramus, NJ
ABSTRACT Conversion of roller pump flow to
pulsatile flow by the pulsatile assist device (PAD) is said to result in improved myocardial preservation and a decrease in the incidence of perioperative myocardial infarction. The clinical advantages of the PAD were evaluated in a prospective randomized study of 100 consecutive coronary artery bypass operations. Serial electrocardiograms, creatine phosphokinase isoenzyme studies, and myocardial scans with technetium-labeled pyrophosphate failed to demonstrate any significant difference between patients with the PAD and those receiving nonpulsatile flow. Plasma hemoglobin levels were significantly higher in the PAD group indicating increased blood trauma. Other potential disadvantages of the PAD are discussed. Based on this study, we see few advantages of the PAD in routine coronary bypass operations.
It has been reported that conversion of nonpulsatile roller pump flow to pulsatile flow by the pulsatile assist device (PAD) offers several advantages [l-41. Bregman and associates [ll suggested that the PAD provides improved myocardial preservation and a decreased incidence of perioperative myocardial infarction, but there have been no controlled clinical studies to support their conclusions. In a previous retrospective evaluation [ll], we could find few advantages of the PAD over nonpulsatile pump flow during coronary bypass procedures. The present study was performed in a prospective randomized fashion to better delineate the effect of the PAD on myocardial preservation and perioperative myocardial infarction during coronary bypass operations. From the Thoracic Surgical Service, University Hospital, Augusta, GA.
269 0003-49751791090269-05$01.25 @ 1978 by G. Lionel Zumbro
270 The Annals of Thoracic Surgery Vol 28 No 3 September 1979
Characteristics of Study Groups Variable Mean age (yrs) Sex Ejection fraction > 5O0/oa Mean cardiopulmonary bypass timeb (min) Mean cross-clamp timeb (min) Mean number grafts per patient Left main coronary occlusiona
Without PAD
With PAD 54 8 women; 42 men 40 patients 102 f 41 24 11 3.6 9 patients
55 8 women; 42 men 42 patients 89 f 33 27 13 3.5 10 patients
+
+
aChi square less than 1 with 1 degree of freedom, no significant difference. bStudent paired t test, no significant difference (p > 0.05). PAD = pulsatile assist device.
sis of variance [9]. Statistical significance was indicated by a p value < 0.05. The characteristics of each study group are shown in the Table. Age and sex were similar in each group. Pump time was slightly longer in the PAD group; however, this difference was not statistically significant ( p > 0.05). Average ischemia time was similar in each group. The number of bypass grafts ranged from 1to 9 with a mean of 3.6 grafts per patient in the PAD group and 3.5 grafts per patient in the group receiving nonpulsatile perfusion. Twenty percent of each group had 50% or greater narrowing of the diameter of the left main coronary artery.
Results There were no operative deaths in either group. The intraaortic balloon was not required for any patient. However, 2 patients in the PAD group received 10 to 15 minutes of additional PAD support following cessation of cardiopulmonary bypass because of an initially high left atrial pressure (greater than 20 mm Hg) associated with a low systemic arterial pressure. There were two (4%) perioperative infarcts in the nonpulsatile flow group and three (6%) in the PAD group. Continuous inotropic drips were necessary in 2 (4%) patients in the PAD group and 1(2%)patient in the group receiving nonpulsatile flow. Transient intraventricular conduction defects (left bundle-branch block, right bundle-branch block, or left anterior hemiblock) occurred in 7 (14%) patients receiving pulsatile flow and 8 (16%) patients receiving nonpulsatile flow. Transient S-T segment depression of 2 mm or more was seen in 8
c--t \
Creatine phosphokinase II isoenzyme levels following coronary artery bypass operation in two groups of patients, one group receiving pulsatile perfusion with a pulsatile assist device (PAD) and one group receiving nonpulsatile perfusion. (" = Fixed effects analysis of variance, no statistically significant difference.)
patients (16%) in the PAD group and 4 patients (8%) in the other group. CPK I1 isoenzyme levels are shown in the Figure. There was no statistically significant difference in CPK I1 isoenzyme levels immedi-
271 Zumbro et al: Pulsatile Assist Device
ately after operation and 24 and 48 hours after operation. Significant S-T segment depression was more common in the group receiving pulsatile flow but was not statistically significant. There was also no difference in the need for inotropic support while the patients were being weaned from cardiopulmonary bypass. Free plasma hemoglobin levels were significantly higher in the PAD group compared with the group receiving nonpulsatile perfusion: 80 k 40 mg per 100 ml and 56 k 29 mg per 100 ml, respectively ( p < 0.01). There was no significant difference in platelet levels following cardiopulmonary bypass: 159, 170/mm3for the PAD group and 164, 841/mm3for the other group. An inadequate pulse pressure (less than 30 mm Hg) with the PAD occurred in 5 (10%) patients. On one occasion, extremely high line pressures developed and the PAD was discontinued.
Comment It is well recognized that pulsatile perfusion during cardiopulmonary bypass is physiologically better for organ perfusion than nonpulsatile pump flow. However, creation of pulsatile flow from standard roller pump flow has numerous disadvantages, including blood trauma and increased cost and complexity [5, 111. Pappas demonstrated the effectiveness of using an intraaortic balloon to create pulsatile cardiopulmonary bypass [6, 71. However, the attendant morbidity associated with insertion of the balloon into the femoral artery militates against its routine use to create pulsatile cardiopulmonary bypass. The PAD was the first simple clinical in-line device that produced pulsatile pump flow [l-3, 51. It offered the additional advantage of temporary counterpulsation following cessation of bypass. Since the surgeon in this study (G. L. Z.) utilized brief periods of intermittent ischemic arrest, it appeared the PAD was ideally suited to provide periods of pulsatile flow to the myocardium each time the aortic cross-clamp was removed. This was believed to be especially true during periods of ventricular fibrillation since experimental studies have shown improved subendocardial perfusion with pulsatile flow during ventricular fibrillation [8].
A previous retrospective study by us failed to demonstrate any significant clinical advantage of the PAD in day-to-day routine coronary bypass procedures [ill. Moreover, our earlier experience had directed attention to potential PAD-related problems. These include the possibility of a fractured aorta at the site of crossclamping, instability of the aortic cannula, the possibility of gaseous emboli during the negative phase of pulsation, occasional inconsistent counterpulsation, increased cost and complexity of the line, and increased trauma to blood. This prospective randomized study was performed to obtain objective information concerning the benefits of the PAD in offering myocardial protection during routine coronary bypass procedures. As judged by the clinical variables measured in this study, there is no discernible advantage to using the PAD for routine coronary operations. In fact, there are some disadvantages, most notably increased hemolysis and increased cost and complexity of the perfusion lines. Another problem that concerns us and other investigators [lo, 111 is gaseous emboli seen during the negative phase of pulsation while the pump lines are being recirculated. Gaseous emboli detected in vitro may not be present in vivo. Further studies should be done to establish the safety of negative phase pulsation with respect to gaseous embolization. Instability of the aortic cannula is a potential problem during pulsation and requires special attention to the securing of the arterial cannula. A final disadvantage is the possibility of transection of the aorta at the cross-clamp site. In our earlier study [111 3 patients sustained near total transection. Subsequently, we have turned the PAD off during the period of clamping the aorta and have not had a recurrence of this complication. Because of the popularity of current techniques of cold cardioplegic myocardial preservation, the primary advantages of the PAD are improved peripheral organ perfusion and counterpulsation capability following cessation of cardiopulmonary bypass. In view of the increased cost accompanying usage of the PAD, lack of evidence of myocardial protection demonstrated in this study, and possibility of gaseous emboli and increased blood trauma, we
272 The Annals of Thoracic Surgery Vol 28 No 3 September 1979
have discontinued use of t h e PAD in routine coronary bypass operations. We still consider use of the PAD in the extremely high-risk patient who is likely to require a period Of ‘Oun-
terpulsation
cessation
Of
cardiopul-
monary bypass.
References 1. Bregman D, Bailin M, Bowman FO Jr, et al: A pulsatile assist device for use during cardiopulmonary bypass. Ann Thorac Surg 24:574, 1977 2. Bregman D, Bowman FO Jr, Parodi EN, et al: An improved method of myocardial protection with pulsation during cardiopulmonary bypass. Circulation: Suppl 2:56:157, 1977 3. Bregman D, Parodi EN, Haubert SM, et al: Counterpulsation with a new pulsatile assist device (PAD) in open heart surgery. Med Instrum 10:232, 1976 4. Kaplitt MJ, Tamari Y: Clinical experience with the Tamari-Kaplitt pulsator: a new device to create pulsatile flow or counterpulsation during open heart surgery (abstract). Am J Cardiol 39: 260, 1977 5 . Mavroudis C: To pulse or not to pulse. Ann Thorac Surg 25:259, 1978 6. Pappas G: A simple method of producing pulsatile flow during clinical cardiopulmonary bypass. Ann Thorac Surg 17:405, 1974 7. Pappas G: Intrathoracic intra-aortic balloon insertion for pulsatile cardiopulmonary bypass. Arch Surg 109:842, 1974 8. Steed DL, Follette DM, Foglia R, et al: Effects of pulsatile assistance and nonpulsatile flow on subendocardial perfusion during cardiopulmonary bypass. Ann Thorac Surg 26:133, 1978 9. Winer BJ: Statistical Principles in Experimental Designing. New York, McGraw-Hill, 1962, pp 228-241 10. Wise EA, Mandl JP, Zaayer WE: Gaseous emboli generation by a pulsatile assist device. J Extracorp Tech 10:93, 1978 11. Zumbro GL, Shearer G, Fishback ME, et al: A critical look at the pulsatile assist device (PAD) (abstract). Chest 74:354, 1978
Discussion (New York, NY): A safe and simple method of creating pulsatile cardiopulmonary bypass is now available on a routine basis for clinical use. Certainly, since our initial description of the pulsatile assist device at this meeting in 1977, our experience with more than 600 patients at the Columbia-Presbyterian Medical Center has supported this statement. In spite of the fact that Dr. Zumbro and his colleagues have not been able to reproduce our data, we
DR. DAVID BREGMAN
have consistently shown the following effects of pulsatile flow: First, pulsatile flow increases urinary output and has virtually eliminated postoperative renal failure. We have not seen one case of pure postoperative renal failure among our last 600 patients receiving pulsatile flow. By not providing pulsatile flow during cross-clamping and by failing to achieve physiological pulse pressures of 40 to 50 mm Hg in approximately 20% of his patients, Dr. Zumbro has minimized this most published and widely quoted advantage of pulsatile flow. The size of the aortic cannula, which was not stated, is extremely important. Cannulas less than 24F increase hemolysis, and with them it usually is not possible to achieve physiological pulse pressures. The small size of Dr. Zumbro’s clinical series coupled with their normal left ventricular function makes i t hard to draw any firm conclusions on the benefits or disadvantages of pulsatile cardiopulmonary bypass either on the heart or on the periphery. Second, stroke and other neurological complications of cardiopulmonary bypass are minimized with pulsatile flow. There was only one cerebrovascular accident in our clinical series of 600 patients. Therefore, the allusion to one study suggesting that the pulsatile assist device causes gaseous emboli seems unfounded, especially since the entire experimental design of that study is open to question. Third, the use of intraaortic balloon pumping after operation has been markedly decreased in our series of patients receiving pulsatile flow, even in patients with preoperative impaired left ventricular function who comprised three-quarters of our clinical series. We have now minimized preoperative intraaortic balloon pumping and, in fact, have employed intraaortic balloon pumping only seven times postoperatively in 600 patients. Six of the 7 patients were weaned from the balloon and were discharged from the hospital. Other clinical observations in our series include a decrease in peripheral vascular resistance, minimal subendocardial ischemia, a decreased time for normalization of S-T segment and T wave changes after cross-clamping, a decrease in postoperative myocardial infarction (currently our rate of perioperative infarction is 1.8% in this entire series), a marked decrease in the postoperative requirement for inotropic support, a decreased time for cooling and rewarming during cardiopulmonary bypass, a decreased time for weaning from cardiopulmonary bypass patients who have impaired left ventricular function, and a shorter stay in the postoperative intensive care unit. Clearly, the issue of pulsatile flow is not settled. However, it is our current belief that in 1979, the best myocardial protection for a patient with a depressed or impaired left ventricle undergoing an open-heart operation is to employ hypothermia and cold potas-
273 Zumbro et al: Pulsatile Assist Device
sium cardioplegia, and to reperfuse with synchronous pulsatile perfusion in an empty beating heart. (Manhasset, NY): In 1974, we described the concept of an in-line device for the express purpose of providing counterpulsation before and after bypass at the flip of a switch and without the need to insert an intraaortic balloon pump at the end of a cardiopulmonary run. It was our belief that if such a device were to be useful to the cardiac surgeon, it would have to be safe, simple, effective, and inexpensive. These elements would allow it to be employed in most patients since the surgeon could not anticipate those patients who might run into difficulty on the pump. The device we have employed in more than 300 patients consists essentially of a piece of Tygon tubing that has been expanded in its central portion, through a system of heat and pressure, so as to provide compressibility. It is very important to understand that this is a single-unit construction with no joints, no connections, and no fusion points. It is merely a single piece of tubing run in and out of an external housing so that the central part can be compressed. With regard to pulsatile bypass, which is a completely different discussion from the original concept of having a simple device in the line for counterpulsation, I would point out that during the recovery phase from cardioplegia, good pulsatile flow can be provided in a counterpulsating mode so that the peak pressures come in diastole and a good wave form is produced. We did not utilize a pulsatile flow routinely throughout the run in all elective cases despite the fact that the device is in the line. As for the marked variability in pulsatile flow, both with regard to the variability of creating pulsatile flow as well as some of the complications that Dr. Zumbro encountered, there is a marked difference in construction among the devices. That used by Dr. Zumbro, the one Dr. Murphy has used, and the device that we have been using are quite unlike. One difference is critical. What we call a thin outlet device of the type used by Dr. Zumbro and his group can collapse at its joint before it exits from the housing and cause a shuddering and fluttering effect. Dr. Zumbro’s group noted this and concluded there was instability of the aortic cannula and the possibility of intimal injury. In contrast, a thick outlet tubing, like the Tygon tubing we have been using, does not collapse at its outlet when pressure is introduced, and gives a more uniform type of pulsatile effect. DR. MARTIN J. KAPLITT
With regard to hemolysis, I think that in addition to the size of the aortic cannula, it should be pointed out that there is no need to squeeze the device so that its walls touch and thereby damage the formed elements of the blood. Because there is no need to squeeze the device empty, thereby creating hemolysis unnecessarily, care should be taken to see how much pressure is being applied. DR. ZUMBRO: I appreciate Dr. Bregman’s comments. However, we disagree in many aspects concerning the efficacy of the pulsatile assist device. Only 10% of our patients had ineffective pulsation of less than a 30 mm pulse pressure. I do not believe that it has been clearly demonstrated that the pulsatile assist device decreases the instance of renal failure. In my experience, it has offered no advantage in patients with compromised renal function. However, it is true that patients receiving pulsatile flow do show increased urine output during the pump run. We routinely use a 24F angled cannula, which is more than adequate in diameter to receive a good pulse pressure from the pulsatile assist device. We have observed subsequently that an angled cannula flutters more than a straight cannula and could be a factor in creating increased hemolysis when pulsatile flow is utilized. Of our patients, 20% did have significant impairment of ventricular function and an additional 20% had a diseased left main coronary artery. I believe this represents a significant number of high-risk patients and probably reflects a cross section of patients undergoing coronary operation every day in the United States. I don’t believe there is data to support reperfusion of the beating heart with pulsatile flow. A paper presented to this Society last year suggested the benefits of pulsatile flow are seen primarily in the fibrillating heart. I have personally used Dr. Kaplitt’s pulsator on one occasion. It is clearly a different device. The entrance and exit areas of the Kaplitt device consist of thicker tubing and do not collapse during pulsation as the Datascope device certainly does. Negative phase pulsation is not necessary and, in my opinion, can be hazardous particularly if there is a small leak in the pump tubing proximal to the device. This can result in aspirating air into the arterial line, producing air embolism. Although we have not seen this occur clinically, it continues to be of great concern to us. In general, with the current, cold cardioplegic techniques, I see few advantages to the additional cost and complexity of pulsatile assist devices.
Presented at the Fifteenth Annual Meeting of The Society of Thoracic Surgeons, Jan 15-17, 1979, Phoenix, AZ.
Materials and Methods From October, 1977, to May, 1978, 100 consecutive patients undergoing coronary artery bypass operation were randomized prospectively. Fifty patients received nonpulsatile perfusion and 50 received pulsatile perfusion produced by the PAD.* All operations were performed by the same primary surgeon ( G . L. Z .) utilizing intermittent ischemic arrest and moderate systemic hypothermia (28" to 30°C). The PAD was turned off while the aorta was clamped to avoid intimal injury. Saphenous veins were utilized almost exclusively. Only 6 patients received an internal mammary graft. All distal anastomoses were performed first with the patient on cardiopulmonary bypass, and proximal anastomoses were performed last while the patient was being rewarmed. Perioperative myocardial injury was evaluated by serial electrocardiograms and creatine phosphokinase (CPK) I1 isoenzyme studies performed immediately after operation and for the first three postoperative days. Myocardial scans with technetium 99m-labeled pyrophosphate were done between the second and fourth postoperative days. Patients were considered to have sustained a perioperative myocardial infarction if the ECG demonstrated new Q waves, loss of R wave progression or permanent conduction defects. Patients with positive myocardial scans were considered to have sustained a perioperative myocardial infarction regardless of ECG findings. Lesser degrees of myocardial injury were evaluated by S-T segment depression of 2 mm or more and CPK I1 isoenzyme levels. Blood trauma was evaluated by measuring free plasma hemoglobin and platelet counts immediately following operation. Data were analyzed by the Student t test, standard chi-square test, or fixed effects analy-
Address reprint requests to Dr. Zumbro, Suite 2-D, 820 St. Sebastian Way, Augusta, GA 30902.
"Datascope Corp., Paramus, NJ
ABSTRACT Conversion of roller pump flow to
pulsatile flow by the pulsatile assist device (PAD) is said to result in improved myocardial preservation and a decrease in the incidence of perioperative myocardial infarction. The clinical advantages of the PAD were evaluated in a prospective randomized study of 100 consecutive coronary artery bypass operations. Serial electrocardiograms, creatine phosphokinase isoenzyme studies, and myocardial scans with technetium-labeled pyrophosphate failed to demonstrate any significant difference between patients with the PAD and those receiving nonpulsatile flow. Plasma hemoglobin levels were significantly higher in the PAD group indicating increased blood trauma. Other potential disadvantages of the PAD are discussed. Based on this study, we see few advantages of the PAD in routine coronary bypass operations.
It has been reported that conversion of nonpulsatile roller pump flow to pulsatile flow by the pulsatile assist device (PAD) offers several advantages [l-41. Bregman and associates [ll suggested that the PAD provides improved myocardial preservation and a decreased incidence of perioperative myocardial infarction, but there have been no controlled clinical studies to support their conclusions. In a previous retrospective evaluation [ll], we could find few advantages of the PAD over nonpulsatile pump flow during coronary bypass procedures. The present study was performed in a prospective randomized fashion to better delineate the effect of the PAD on myocardial preservation and perioperative myocardial infarction during coronary bypass operations. From the Thoracic Surgical Service, University Hospital, Augusta, GA.
269 0003-49751791090269-05$01.25 @ 1978 by G. Lionel Zumbro
270 The Annals of Thoracic Surgery Vol 28 No 3 September 1979
Characteristics of Study Groups Variable Mean age (yrs) Sex Ejection fraction > 5O0/oa Mean cardiopulmonary bypass timeb (min) Mean cross-clamp timeb (min) Mean number grafts per patient Left main coronary occlusiona
Without PAD
With PAD 54 8 women; 42 men 40 patients 102 f 41 24 11 3.6 9 patients
55 8 women; 42 men 42 patients 89 f 33 27 13 3.5 10 patients
+
+
aChi square less than 1 with 1 degree of freedom, no significant difference. bStudent paired t test, no significant difference (p > 0.05). PAD = pulsatile assist device.
sis of variance [9]. Statistical significance was indicated by a p value < 0.05. The characteristics of each study group are shown in the Table. Age and sex were similar in each group. Pump time was slightly longer in the PAD group; however, this difference was not statistically significant ( p > 0.05). Average ischemia time was similar in each group. The number of bypass grafts ranged from 1to 9 with a mean of 3.6 grafts per patient in the PAD group and 3.5 grafts per patient in the group receiving nonpulsatile perfusion. Twenty percent of each group had 50% or greater narrowing of the diameter of the left main coronary artery.
Results There were no operative deaths in either group. The intraaortic balloon was not required for any patient. However, 2 patients in the PAD group received 10 to 15 minutes of additional PAD support following cessation of cardiopulmonary bypass because of an initially high left atrial pressure (greater than 20 mm Hg) associated with a low systemic arterial pressure. There were two (4%) perioperative infarcts in the nonpulsatile flow group and three (6%) in the PAD group. Continuous inotropic drips were necessary in 2 (4%) patients in the PAD group and 1(2%)patient in the group receiving nonpulsatile flow. Transient intraventricular conduction defects (left bundle-branch block, right bundle-branch block, or left anterior hemiblock) occurred in 7 (14%) patients receiving pulsatile flow and 8 (16%) patients receiving nonpulsatile flow. Transient S-T segment depression of 2 mm or more was seen in 8
c--t \
Creatine phosphokinase II isoenzyme levels following coronary artery bypass operation in two groups of patients, one group receiving pulsatile perfusion with a pulsatile assist device (PAD) and one group receiving nonpulsatile perfusion. (" = Fixed effects analysis of variance, no statistically significant difference.)
patients (16%) in the PAD group and 4 patients (8%) in the other group. CPK I1 isoenzyme levels are shown in the Figure. There was no statistically significant difference in CPK I1 isoenzyme levels immedi-
271 Zumbro et al: Pulsatile Assist Device
ately after operation and 24 and 48 hours after operation. Significant S-T segment depression was more common in the group receiving pulsatile flow but was not statistically significant. There was also no difference in the need for inotropic support while the patients were being weaned from cardiopulmonary bypass. Free plasma hemoglobin levels were significantly higher in the PAD group compared with the group receiving nonpulsatile perfusion: 80 k 40 mg per 100 ml and 56 k 29 mg per 100 ml, respectively ( p < 0.01). There was no significant difference in platelet levels following cardiopulmonary bypass: 159, 170/mm3for the PAD group and 164, 841/mm3for the other group. An inadequate pulse pressure (less than 30 mm Hg) with the PAD occurred in 5 (10%) patients. On one occasion, extremely high line pressures developed and the PAD was discontinued.
Comment It is well recognized that pulsatile perfusion during cardiopulmonary bypass is physiologically better for organ perfusion than nonpulsatile pump flow. However, creation of pulsatile flow from standard roller pump flow has numerous disadvantages, including blood trauma and increased cost and complexity [5, 111. Pappas demonstrated the effectiveness of using an intraaortic balloon to create pulsatile cardiopulmonary bypass [6, 71. However, the attendant morbidity associated with insertion of the balloon into the femoral artery militates against its routine use to create pulsatile cardiopulmonary bypass. The PAD was the first simple clinical in-line device that produced pulsatile pump flow [l-3, 51. It offered the additional advantage of temporary counterpulsation following cessation of bypass. Since the surgeon in this study (G. L. Z.) utilized brief periods of intermittent ischemic arrest, it appeared the PAD was ideally suited to provide periods of pulsatile flow to the myocardium each time the aortic cross-clamp was removed. This was believed to be especially true during periods of ventricular fibrillation since experimental studies have shown improved subendocardial perfusion with pulsatile flow during ventricular fibrillation [8].
A previous retrospective study by us failed to demonstrate any significant clinical advantage of the PAD in day-to-day routine coronary bypass procedures [ill. Moreover, our earlier experience had directed attention to potential PAD-related problems. These include the possibility of a fractured aorta at the site of crossclamping, instability of the aortic cannula, the possibility of gaseous emboli during the negative phase of pulsation, occasional inconsistent counterpulsation, increased cost and complexity of the line, and increased trauma to blood. This prospective randomized study was performed to obtain objective information concerning the benefits of the PAD in offering myocardial protection during routine coronary bypass procedures. As judged by the clinical variables measured in this study, there is no discernible advantage to using the PAD for routine coronary operations. In fact, there are some disadvantages, most notably increased hemolysis and increased cost and complexity of the perfusion lines. Another problem that concerns us and other investigators [lo, 111 is gaseous emboli seen during the negative phase of pulsation while the pump lines are being recirculated. Gaseous emboli detected in vitro may not be present in vivo. Further studies should be done to establish the safety of negative phase pulsation with respect to gaseous embolization. Instability of the aortic cannula is a potential problem during pulsation and requires special attention to the securing of the arterial cannula. A final disadvantage is the possibility of transection of the aorta at the cross-clamp site. In our earlier study [111 3 patients sustained near total transection. Subsequently, we have turned the PAD off during the period of clamping the aorta and have not had a recurrence of this complication. Because of the popularity of current techniques of cold cardioplegic myocardial preservation, the primary advantages of the PAD are improved peripheral organ perfusion and counterpulsation capability following cessation of cardiopulmonary bypass. In view of the increased cost accompanying usage of the PAD, lack of evidence of myocardial protection demonstrated in this study, and possibility of gaseous emboli and increased blood trauma, we
272 The Annals of Thoracic Surgery Vol 28 No 3 September 1979
have discontinued use of t h e PAD in routine coronary bypass operations. We still consider use of the PAD in the extremely high-risk patient who is likely to require a period Of ‘Oun-
terpulsation
cessation
Of
cardiopul-
monary bypass.
References 1. Bregman D, Bailin M, Bowman FO Jr, et al: A pulsatile assist device for use during cardiopulmonary bypass. Ann Thorac Surg 24:574, 1977 2. Bregman D, Bowman FO Jr, Parodi EN, et al: An improved method of myocardial protection with pulsation during cardiopulmonary bypass. Circulation: Suppl 2:56:157, 1977 3. Bregman D, Parodi EN, Haubert SM, et al: Counterpulsation with a new pulsatile assist device (PAD) in open heart surgery. Med Instrum 10:232, 1976 4. Kaplitt MJ, Tamari Y: Clinical experience with the Tamari-Kaplitt pulsator: a new device to create pulsatile flow or counterpulsation during open heart surgery (abstract). Am J Cardiol 39: 260, 1977 5 . Mavroudis C: To pulse or not to pulse. Ann Thorac Surg 25:259, 1978 6. Pappas G: A simple method of producing pulsatile flow during clinical cardiopulmonary bypass. Ann Thorac Surg 17:405, 1974 7. Pappas G: Intrathoracic intra-aortic balloon insertion for pulsatile cardiopulmonary bypass. Arch Surg 109:842, 1974 8. Steed DL, Follette DM, Foglia R, et al: Effects of pulsatile assistance and nonpulsatile flow on subendocardial perfusion during cardiopulmonary bypass. Ann Thorac Surg 26:133, 1978 9. Winer BJ: Statistical Principles in Experimental Designing. New York, McGraw-Hill, 1962, pp 228-241 10. Wise EA, Mandl JP, Zaayer WE: Gaseous emboli generation by a pulsatile assist device. J Extracorp Tech 10:93, 1978 11. Zumbro GL, Shearer G, Fishback ME, et al: A critical look at the pulsatile assist device (PAD) (abstract). Chest 74:354, 1978
Discussion (New York, NY): A safe and simple method of creating pulsatile cardiopulmonary bypass is now available on a routine basis for clinical use. Certainly, since our initial description of the pulsatile assist device at this meeting in 1977, our experience with more than 600 patients at the Columbia-Presbyterian Medical Center has supported this statement. In spite of the fact that Dr. Zumbro and his colleagues have not been able to reproduce our data, we
DR. DAVID BREGMAN
have consistently shown the following effects of pulsatile flow: First, pulsatile flow increases urinary output and has virtually eliminated postoperative renal failure. We have not seen one case of pure postoperative renal failure among our last 600 patients receiving pulsatile flow. By not providing pulsatile flow during cross-clamping and by failing to achieve physiological pulse pressures of 40 to 50 mm Hg in approximately 20% of his patients, Dr. Zumbro has minimized this most published and widely quoted advantage of pulsatile flow. The size of the aortic cannula, which was not stated, is extremely important. Cannulas less than 24F increase hemolysis, and with them it usually is not possible to achieve physiological pulse pressures. The small size of Dr. Zumbro’s clinical series coupled with their normal left ventricular function makes i t hard to draw any firm conclusions on the benefits or disadvantages of pulsatile cardiopulmonary bypass either on the heart or on the periphery. Second, stroke and other neurological complications of cardiopulmonary bypass are minimized with pulsatile flow. There was only one cerebrovascular accident in our clinical series of 600 patients. Therefore, the allusion to one study suggesting that the pulsatile assist device causes gaseous emboli seems unfounded, especially since the entire experimental design of that study is open to question. Third, the use of intraaortic balloon pumping after operation has been markedly decreased in our series of patients receiving pulsatile flow, even in patients with preoperative impaired left ventricular function who comprised three-quarters of our clinical series. We have now minimized preoperative intraaortic balloon pumping and, in fact, have employed intraaortic balloon pumping only seven times postoperatively in 600 patients. Six of the 7 patients were weaned from the balloon and were discharged from the hospital. Other clinical observations in our series include a decrease in peripheral vascular resistance, minimal subendocardial ischemia, a decreased time for normalization of S-T segment and T wave changes after cross-clamping, a decrease in postoperative myocardial infarction (currently our rate of perioperative infarction is 1.8% in this entire series), a marked decrease in the postoperative requirement for inotropic support, a decreased time for cooling and rewarming during cardiopulmonary bypass, a decreased time for weaning from cardiopulmonary bypass patients who have impaired left ventricular function, and a shorter stay in the postoperative intensive care unit. Clearly, the issue of pulsatile flow is not settled. However, it is our current belief that in 1979, the best myocardial protection for a patient with a depressed or impaired left ventricle undergoing an open-heart operation is to employ hypothermia and cold potas-
273 Zumbro et al: Pulsatile Assist Device
sium cardioplegia, and to reperfuse with synchronous pulsatile perfusion in an empty beating heart. (Manhasset, NY): In 1974, we described the concept of an in-line device for the express purpose of providing counterpulsation before and after bypass at the flip of a switch and without the need to insert an intraaortic balloon pump at the end of a cardiopulmonary run. It was our belief that if such a device were to be useful to the cardiac surgeon, it would have to be safe, simple, effective, and inexpensive. These elements would allow it to be employed in most patients since the surgeon could not anticipate those patients who might run into difficulty on the pump. The device we have employed in more than 300 patients consists essentially of a piece of Tygon tubing that has been expanded in its central portion, through a system of heat and pressure, so as to provide compressibility. It is very important to understand that this is a single-unit construction with no joints, no connections, and no fusion points. It is merely a single piece of tubing run in and out of an external housing so that the central part can be compressed. With regard to pulsatile bypass, which is a completely different discussion from the original concept of having a simple device in the line for counterpulsation, I would point out that during the recovery phase from cardioplegia, good pulsatile flow can be provided in a counterpulsating mode so that the peak pressures come in diastole and a good wave form is produced. We did not utilize a pulsatile flow routinely throughout the run in all elective cases despite the fact that the device is in the line. As for the marked variability in pulsatile flow, both with regard to the variability of creating pulsatile flow as well as some of the complications that Dr. Zumbro encountered, there is a marked difference in construction among the devices. That used by Dr. Zumbro, the one Dr. Murphy has used, and the device that we have been using are quite unlike. One difference is critical. What we call a thin outlet device of the type used by Dr. Zumbro and his group can collapse at its joint before it exits from the housing and cause a shuddering and fluttering effect. Dr. Zumbro’s group noted this and concluded there was instability of the aortic cannula and the possibility of intimal injury. In contrast, a thick outlet tubing, like the Tygon tubing we have been using, does not collapse at its outlet when pressure is introduced, and gives a more uniform type of pulsatile effect. DR. MARTIN J. KAPLITT
With regard to hemolysis, I think that in addition to the size of the aortic cannula, it should be pointed out that there is no need to squeeze the device so that its walls touch and thereby damage the formed elements of the blood. Because there is no need to squeeze the device empty, thereby creating hemolysis unnecessarily, care should be taken to see how much pressure is being applied. DR. ZUMBRO: I appreciate Dr. Bregman’s comments. However, we disagree in many aspects concerning the efficacy of the pulsatile assist device. Only 10% of our patients had ineffective pulsation of less than a 30 mm pulse pressure. I do not believe that it has been clearly demonstrated that the pulsatile assist device decreases the instance of renal failure. In my experience, it has offered no advantage in patients with compromised renal function. However, it is true that patients receiving pulsatile flow do show increased urine output during the pump run. We routinely use a 24F angled cannula, which is more than adequate in diameter to receive a good pulse pressure from the pulsatile assist device. We have observed subsequently that an angled cannula flutters more than a straight cannula and could be a factor in creating increased hemolysis when pulsatile flow is utilized. Of our patients, 20% did have significant impairment of ventricular function and an additional 20% had a diseased left main coronary artery. I believe this represents a significant number of high-risk patients and probably reflects a cross section of patients undergoing coronary operation every day in the United States. I don’t believe there is data to support reperfusion of the beating heart with pulsatile flow. A paper presented to this Society last year suggested the benefits of pulsatile flow are seen primarily in the fibrillating heart. I have personally used Dr. Kaplitt’s pulsator on one occasion. It is clearly a different device. The entrance and exit areas of the Kaplitt device consist of thicker tubing and do not collapse during pulsation as the Datascope device certainly does. Negative phase pulsation is not necessary and, in my opinion, can be hazardous particularly if there is a small leak in the pump tubing proximal to the device. This can result in aspirating air into the arterial line, producing air embolism. Although we have not seen this occur clinically, it continues to be of great concern to us. In general, with the current, cold cardioplegic techniques, I see few advantages to the additional cost and complexity of pulsatile assist devices.