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Ann Thorac Surg 2000;69:536-540
© 2000 The Society of Thoracic Surgeons

Original Articles

Influence of biopump with and without intraaortic balloon on the coronary and carotid flow

Paulo M. Pêgo-Fernandes, MD, PhDa, Noedir A.G. Stolf, MD, PhDa, Luiz Felipe P. Moreira, MD, PhDa, Helio A. Fabri, MDa, Adolfo A. Leirner, MD, PhDa, Sergio A. Oliveira, MD, PhDa, Adib D. Jatene, MD, PhDa

a Heart Institute of University of São Paulo Medical School, São Paulo, Brazil

Address reprint requests to Dr Pêgo-Fernandes, Instituto do Coração do Hospital das Clínicas da Universidade de São Paulo, Divisão Cirúrgica, 2nd andar Av Dr Eneas de Carvalho Aguiar, 44, São Paulo-SP, Brazil, CEP 05403-000
e-mail: paulopego{at}incor.usp.br


   Abstract
Top
 Abstract
Introduction
 Material and methods
 Results
 Comment
 References
 
Background. The objective of this study was to evaluate the influence of biopump used for left ventricular assistance on the coronary and carotid flows in dogs with normal heart. The efficacy of the simultaneous use of an intraaortic balloon pump to compensate the possible deleterious effects of the circulatory assistance with continuous flow was also analyzed.

Methods. Fifteen dogs were studied. The hemodynamic evaluation included serial measurements of the classic parameters. Carotid and coronary blood flows were obtained by electromagnetic transducers.

Results. The hemodynamic evaluation did not show significant statistical changes. The use of circulatory-isolated assistance with biopump shows reduction (24.6% ± 6.1%) in coronary flow, in relation to the control situation and the concomitant use of biopump and intraaortic balloon pump showed similar coronary flow. Regarding carotid flow, a similar trend was observed in relation to the positive influence of the pulsatile flow with an intraaortic balloon pump without statistical significance (p = 0.0582).

Conclusions. The biopump reduces the coronary flow in dogs. The use of intraaortic balloon pump with the biopump increases the coronary flow significantly, reaching similar values to those observed without the circulatory assistance.


   Introduction
Top
 Abstract
 Introduction
Material and methods
 Results
 Comment
 References
 
Several investigators [1, 2] have reported that mechanical pulsatile flow produce better results than continuous flow devices in ventricular assistance, especially in the medium and long term. On the other hand, the fact that pulsatile flow-producing devices, such as artificial ventricles and total artificial hearts, are usually more complex and expensive than continuous flow devices, with a more complicated handling and a potential to produce more hematologic complications, has to be considered [2].

The concomitant use of an intraaortic balloon pump and a biopump has been studied, as the combination increases the coronary blood flow produced by the intraaortic balloon and increases the arterial blood flow produced by the biopump. It would be even more convenient to combine two easy to handle and inexpensive devices. This would be essential to increase myocardial perfusion to relieve ventricular load and maintain a mean blood pressure and blood flow, allowing the recovery of organ failure, and for the undesirable effects of the continuous biopump flow to be minimized by the pulsatility of the intraaortic balloon pump.

The objective of this study was to evaluate the effects of the centrifugal pump on the coronary and carotid flows in left ventricular circulatory assistance in dogs with normal hearts. In addition, it was aimed at evaluating whether the concomitant use of the intraaortic balloon is sufficient to counterbalance eventual undesirable effects of circulatory assistance with continuous flow.


   Material and methods
Top
 Abstract
 Introduction
 Material and methods
Results
 Comment
 References
 
To achieve our objectives, 19 dogs, with mean weight of 16.3 ± 4.36 kg underwent the experimental procedures, which were carried out at the Bioengineer Division of the Heart Institute, University of São Paulo Medical Center. All animals have received humane care in compliance with the "Guide for the Care and Use of Laboratory Animals" published by the National Institutes of Health (NIH publication 85-23, revised 1985).

The anesthesia technique used hypnotic and halogenated drugs. After tracheal intubation, controlled mechanical ventilation was started. Standardized monitoring included electrocardioscopy, invasive blood pressure (systolic, diastolic, and mean blood pressure), capnography, central venous pressure, central temperature, vesical catheter, and Swan-Ganz catheter.

The experiment included the direct evaluation of coronary artery flow: left coronary artery circumflex branch and the carotid arteries; right carotid artery, with circulatory assistance with a centrifugal pump to the left ventricle, with or without intraaortic balloon assistance.

To measure carotid flow to the right carotid artery, a cervicotomy was performed from the anterior edge of the right sternocleidomastoid muscle, and an extension of 3 cm was released. To measure coronary flow, the heart was approached by a longitudinal thoracotomy with a median sternotomy, while the animal was kept in horizontal dorsal decubitus. The initial portion of the coronary artery circumflex branch was exposed and dissected. Flow rates were recorded with a Hewlett-Packard electromagnetic flowmeter and a Hewlett-Packard polygraph (Hewlett Packard, Waltham, MD).

The intraaortic balloon pump was placed at the thoracic descending aorta, and inserted through the previously dissected left femoral artery. The transsternal access was used to install the biopump, after dissection of the left coronary artery circumflex branch. Two concentric sutures were performed at the beginning of the ascending aorta where a no. 18 infusion cannula was inserted in the middle of the ascending aorta. After a suture was made at the left auricle to insert a -inch cannula. The cannulas are routinely used in cardiac operations and in cases of circulatory assistance with the biopump.

A Biomedicus biopump (Medtronic, Minneapolis, MN) was used. In addition to the measurements of mean coronary and carotid flow, mean right atrial pressure, mean pulmonary capillary pressure, mean pulmonary artery pressure, mean blood pressure, and heart rate were made. Pressure curves were recorded in a Hewlett-Packard polygraph.

To measure the cardiac output a thermodilution technique was used. Cardiac output value, calculated as liters per minute, was obtained by the average of three measurements, as long as the differences among them were less than 10%.

The following hemodynamic parameters were calculated using classic formulas: cardiac index, systolic index, systemic vascular resistance, and pulmonary vascular resistance. All measurements were taken at four time periods: (1) control (C1), the dog has the intraaortic balloon pump and the biopump installed, but they are not in use; (2) biopump test (C2), the intraaortic balloon pump and biopump are installed, but only the biopump is working. This evaluates the isolated effect of the biopump on left ventricular circulatory assistance; (3) biopump and intraaortic balloon pump test (C3), the intraaortic balloon pump and the biopump are working, and the balloon in inflated once at each diastole of the animal’s heart; (4) final condition (C4), the intraaortic balloon pump and the biopump are installed, but only the biopump is working. This condition repeats condition 2 (a second proof condition).

In C2, C3, and C4, the blood flow maintained by the biopump was such that the relation between animal’s blood flow and cardiac output was on average 75%.

The studied variables were presented as mean and standard deviation. Differences between the conditions were evaluated by one-way analysis of variance. The significance level was 0.05.


   Results
Top
 Abstract
 Introduction
 Material and methods
 Results
Comment
 References
 
Fifteen of the 19 experiments were successful. In four animals the experiment was discontinued due to causes leading to the animal’s death or that could have influenced the reliability of the hemodynamic measurements. Arterial gasometry was corrected as needed. Electrolyte measurements were stable and their values were normal. Blood transfusion was required in seven dogs. Hematocrit measurements ranging from 27% to 35% were considered adequate; blood was administered with hematocrit values less than 27% before the beginning of hemodynamic and flow measurements.

Table 1 shows the mean values and standard deviation for the heart rate, mean right atrial pressure, mean pulmonary artery pressure, mean pulmonary capillary pressure, mean blood pressure, cardiac output, cardiac index, systemic vascular resistance, pulmonary vascular resistance. Heart rate was significantly greater in the control animals than in the other three conditions. Statistically significant differences were not found when the three conditions with circulatory assistance were compared to each other.


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  		Table 1. Hemodynamic Parameters Evaluation

 
Right atrial mean pressure was significantly lower in the control condition when compared to the remaining conditions. There was no statistically significant change for this parameter when the three conditions with circulatory assistance were compared to each other.

Pulmonary artery mean pressure was lower in the control animals when compared with C2 (biopump). There was no statistically significant change in the remaining comparisons for this parameter.

Mean pulmonary capillary pressure did not show statistically significant change in the different conditions, as well as the mean blood pressure, cardiac output, cardiac index, systemic vascular resistance, and pulmonary vascular resistance.

Table 2 shows mean values and standard deviation in biopump flows, cardiac output, and biopump flow to total cardiac output ratio (the output produced by the heart in addition to the output produced by the biopump). No statistically significant change for these parameters was observed in the different conditions. The ratio of the biopump mean flow and the total cardiac output was on average 75%.


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  		Table 2. Assisted Circulation Parameters Evaluation

 
For the coronary flow, the profile analysis shows a statistically significant difference among the different conditions (p = 0.0079). Figure 1 shows the coronary flow mean values. C1 is similar to C3 (p = 0.4942). When C2 is compared to C1 (p = 0.0027) and to C3 (p = 0.0023), a significantly lower coronary flow is observed.



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  		Fig 1. Coronary flow evaluation. The flow decreases in C1 and C4 when compared with C1 and C3 (p = 0.0079). (C1 = Control; C2 = Biopump test; C3 = Biopump and intraaortic balloon pump test; C4 = Final.)

 
When C4 result is compared with C3 a statistically significant difference is also observed (p = 0.0118). The result analysis shows the biopump, when working as the single circulatory assistance method, significantly decreased coronary flow (24.6% ± 6.1%). When associated to the intraaortic balloon pump this flow decrease is reversed, returning to baseline values. Therefore, the proof and second proof confirm the statistically significant coronary blood flow decrease with the isolated use of the biopump and the reversal of this decrease with the use of the intraaortic balloon pump.

For the carotid flow, the profile analysis strongly suggests that there is a difference, although not significant (p = 0.0582), among the different steps. In Figure 2 the carotid blood flow may be better visualized in the four conditions. A trend to carotid flow may be observed when C1 is compared to C2 where assisted circulation with the biopump is started (p = 0.0540), and to C4 where the intraaortic balloon is disconnected (p = 0.0602). C1 and C3 have the same results in this parameter (p = 0.8327). A statistically significant difference of the carotid flow is observed when C2 is compared with C3 (p = 0.0298). This reversal of the carotid flow decrease is not confirmed in the final condition (second proof) (p = 0.1186) between C3 and C4, showing this parameter only had a significant trend to decrease with the biopump.



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  		Fig 2. Carotid flow evaluation. There is a tendency of decreased flow in C1 and C4 when compared with C1 and C3 (p = 0.0582). (C1 = Control; C2 = Biopump test; C3 = Biopump and intraaortic balloon pump test; C4 = Final.)

 

   Comment
Top
 Abstract
 Introduction
 Material and methods
 Results
 Comment
References
 
There are no standardized clinical procedures for the use of intraaortic balloon pump and biopump. In cases where the low output is very severe, several surgeons consider the intraaortic balloon pump insufficient to provide hemodynamic stabilization of the patient, and initially use a biopump. There are cases where because of peripheral vascular problems, the insertion of the balloon pump may be extremely difficult and its use is questionable; therefore, the trend is not to use a balloon pump. Our research shows that the combination of the intraaortic balloon pump and the biopump is very useful, especially when the coronary flow is evaluated. It should be emphasized that this combination improves the coronary flow and decreases the cardiac load, once part of the cardiac output is deviated by the biopump. In addition, the afterload decrease produced by the intraaortic balloon pump increases myocardial supply and decreases myocardial demand of oxygen and nutrients. The increased supply combined with decreased demand may be a decisive factor in the patient’s course, especially in an individual who has just undergone surgical trauma and requires time and favorable conditions to recover. Concerning carotid flow, our study suggests a probable improvement with the combination of intraaortic balloon pump and the biopump. Potentially, low cerebral flow manifestations in nonpulsatile flow, for instance, mental confusion that sometimes occurs after the use of extracorporeal circulation, might be minimized by pulsatile flow.

In the English literature, the use of the biopump, a continuous flow device, whether or not used in combination with an intraaortic balloon pump, a pulsatile device, is discussed in a broad manner, pulsatile flow devices versus nonpulsatile flow devices [3, 4]. There are several clinical studies on this issue. Even in acute conditions of mechanical circulatory assistance, as with extracorporeal circulation, there are evaluations comparing the use of pulsatile extracorporeal circulation with continuous flow circulation, which is usually used [5, 6]. Several researchers support the use of pulsatile flow during extracorporeal circulation [5–7], although others consider it absolutely unnecessary [3]. The present study might provide physiopathologic data to explain these differences [7], thanks to better coronary flow resulting from the pulsatility of the intraaortic balloon.

Mickleborough and colleagues [8] subjected two groups of seven dogs to normothermic cardiac arrest to produce myocardial injury and left ventricular insufficiency. Intraaortic balloon pump and inotropic drugs were used in one group of dogs and in the other group, the biopump was used. Both methods achieved good hemodynamic rates at the beginning of left ventricular assistance. However, after 3 hours of assistance, the dogs treated with intraaortic balloon pump and inotropic drugs had lower left ventricular compliance and worse left ventricular systolic function, and a greater degree of necrosis than the group of dogs treated with the biopump. These researchers suggest that even patients who are hemodynamically stable with the use of intraaortic balloon pump and drugs could benefit from early circulatory assistance with the biopump. In our clinical experience at the Heart Institute [9, 10], we observed that late introduction of circulatory assistance devices is an important factor for high morbidity and mortality. However, we believe both methods may be used concurrently in patients where inotropic drugs and intraaortic balloon cannot adequately resolve low cardiac output. This study supports the suggestion made by Pennington’s group: the earlier use of the biopump allows a decrease of ventricular load and produces a better recovery of the insufficient ventricle [11].

Other investigators [12, 13] prefer the concurrent use of mechanical circulatory assistance devices to potentiate the advantages of each method. Ide and colleagues [12] evaluated the use of a catheter combining three ventricular mechanical assistance devices in dogs: the intraaortic balloon pump, the biopump, and the "hemopump." The intraaortic balloon pump was aimed at providing pulsatility to blood flow, and the other devices were continuous flow devices. They studied hemodynamic and myocardial blood flow conditions in 10 dogs with heart failure, comparing these parameters in pulsatile (with intraaortic balloon pump) and nonpulsatile conditions. They concluded that there was improvement in cardiac output, mean aorta pressure, and myocardial blood flow as measured by a Doppler laser flowmeter. This study also highly supports the combination of intraaortic balloon pump and biopump as circulatory assistance devices.

Nagasaka and associates [13] developed a device combining the biopump and a synchronized intraaortic balloon pump. They studied the influence of this device on endocardial viability and renal flow rate. The system was used in 12 pigs and evaluated the devices alone and in combination. The researchers concluded that cardiac assistance was more effective when the two mechanisms were combined, whether or not they were synchronized. Although these studies used different indexes to evaluate the effects on the heart, they corroborate our findings.

Using carotid flow measurements and intermittent hypercapnia, a study with a biopump in 17 calves showed that there was no damage to the cerebral flow autoregulation with the use of continuous flow (fibrillating heart and biventricular assistance with biopump). Onoe and colleagues [14] studied the influence of pulsatile extracorporeal circulation on cerebral blood flow in dogs undergoing periods of circulatory arrest with profound hypothermia, and observed that after circulation resumption, the dogs with pulsatile flow tended to have higher cerebral flow compared to those dogs receiving continuous flow, especially with a longer circulatory arrest time. Sadahiro and associates [15] studied pulsatile and nonpulsatile extracorporeal circulation with normothermia and moderate hypothermia (25°C) in dogs. They observed that the autoregulation of the cerebral flow was kept intact at pressures higher than 50 mm Hg, but below this value the dogs undergoing perfusion with pulsatile flow had a higher cerebral blood flow than the dogs with continuous flow.

In our study, significant carotid blood flow changes were observed when C2 was compared to C3. The significant carotid flow improvement observed with the use of the combination of both methods was not confirmed in the second proof (C4) where the intraaortic balloon pump is turned off. Although there was a trend with p values close to 0.05, the significance level was not achieved probably because the hemodynamic conditions were satisfactory and therefore, did not affect the autoregulation, as shown in other studies.

In summary, (1) left ventricular circulatory assistance with the biopump decreases coronary flow in dogs with normal heart; (2) left ventricular circulatory assistance with the biopump decreased the carotid flow in dogs with normal hearts; (3) the intraaortic balloon pump combined with left ventricular circulatory assistance using a biopump significantly increased the dogs’ coronary flow, achieving similar values to those observed without circulatory assistance; and (4) the intraaortic balloon pump combined with left ventricular circulatory assistance using a biopump tended to normalize the carotid flow in dogs with normal hearts. The intraaortic balloon must be combined with a biopump whenever possible, when it is used for left ventricular circulatory assistance, as it improves coronary flow and consequently myocardial perfusion.


   References
Top
 Abstract
 Introduction
 Material and methods
 Results
 Comment
 References
 

  1. Schoen F.J., Bernhard W.F. Pathological considerations in temporary cardiac assistance. In: Unger F., ed. Assisted circulation 3. Berlin: Springer-Verlag, 1989:103-114.
  2. Unger F. Ventricular assist devices. In: Unger F., ed. Assisted circulation 3. Berlin: Springer-Verlag, 1989:97-102.
  3. Bartlett R.H. Invited letter concerning. J Thorac Cardiovasc Surg 1994;107:644-646.[Free Full Text]
  4. Yozu R., Golding L., Yada I., et al. Do we really need pulse? Chronic nonpulsatile and pulsatile blood flow. Artif Organs 1994;18:638-642.[Medline]
  5. Kirklin J.K., Westaby S., Blackstone E.H., Kirklin J.W., Chenoweth D.E., Pacifico A.D. Complement and the damaging effects of cardiopulmonary bypass. J Thorac Cardiovasc Surg 1983;86:845-857.[Abstract]
  6. Runge T.M., Cohen D.J., Hantler C.B., Bohls F.O., Ottmers S.E., Briceno J.C. Achievement of physiologic pulsatile flow on cardiopulmonary bypass with a 24 French cannula. Trans Am Soc Artif Intern Organs 1992;38:726-729.
  7. Taylor K.M., Bain W.H., Russel M., Brannan J.J., Morton I.J. Peripheral vascular resistance and angiotensin II levels during pulsatile and non-pulsatile cardiopulmonary bypass. Thorax 1979;34:594-598.[Abstract/Free Full Text]
  8. Mickleborough L.L., Rebeyka I., Wilson G.J., Gray G., Desrosiers A. Comparison of left ventricular assist and intra-aortic balloon counterpulsation during early reperfusion after ischemic arrest of the heart. J Thorac Cardiovasc Surg 1987;93:597-608.[Abstract]
  9. Pêgo-Fernandes P.M., Moreira L.F.P., Stolf N.A.G., et al. Assistência circulatória com bomba centrífuga no choque cardiogênico após cirurgia com extracorpórea. Rev Bras Cir Cardiovasc 1991;6:104-108.
  10. Pêgo-Fernandes P.M., Moreira L.F.P., Dallan L.A., et al. Uso de bomba centrífuga no pós-operatório de cirurgia cardíaca. Rev Bras Cir Cardiovasc 1992;7:263-268.
  11. Reedy J.E., Pennington D.G., Miller L.W., et al. Status I heart transplant patients. Conventional vs. ventricular assist device (VAD) support. J Heart Lung Transplant 1992;11:246-252.[Medline]
  12. Ide H., Yamaguchi A., Ino T., et al. Evaluation of the pulsatility of a new pulsatile left ventricular assist device—the integrated cardioassist catheter—in dogs. J Thorac Cardiovasc Surg 1994;107:569-575.[Abstract/Free Full Text]
  13. Nagasaka F., Hasegawa T., Shiono M., Orime Y., Sezai Y. New sequential synchronized driving system of intraaortic balloon pumping and left ventricular assist device. Artif Organs 1992;16:216-218.[Medline]
  14. Onoe M.Y., Mori A., Watarida S., et al. The effect of pulsatile perfusion on cerebral blood flow during profound hypothermia with total circulatory arrest. J Thorac Cardiovasc Surg 1994;108:119-125.[Abstract/Free Full Text]
  15. Sadahiro M., Haneda K., Mohri H. Experimental study of cerebral autoregulation during cardiopulmonary bypass with or without pulsatile perfusion. J Thorac Cardiovasc Surg 1994;108:446-454.[Abstract/Free Full Text]
Accepted for publication July 30, 1999.




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