Ann Thorac Surg 1999;67:1169-1171
© 1999 The Society of Thoracic Surgeons
Case Reports
The use of pulsatile perfusion during aortic valve replacement in pregnancy
Henry F. Tripp, MDa,
Robert M. Stiegel, MDb,
Joseph P. Coyle, MDa,b
a Cardiothoracic Surgery, Brooke Army Medical Center, Fort Sam Houston, Texas, USA
b Carolinas Heart Institute, Carolinas Medical Center, Charlotte, North Carolina, USA
Accepted for publication October 5, 1998.
Address reprint requests to Dr Stiegel, Carolinas Heart Institute, 1000 Blythe Blvd, Charlotte, NC 28203
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Abstract
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Cardiac operations are occasionally required during pregnancy. Despite a low maternal mortality, fetal mortality remains high. Previous reports have suggested maintenance of high perfusion pressure and flow rate as protective measures to maintain fetal viability. Recent experimental data suggest pulsatile perfusion may help preserve placental hemodynamic function. The successful use of pulsatile bypass to replace the aortic valve in a 25-year-old female at 14 weeks gestation, with both maternal and fetal survival, is presented.
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Introduction
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Cardiac disease complicates pregnancy in 2% or more of patients. Valvular disease predominates although aortic disease processes also occur [1,2]. Cardiac surgery can be accomplished with relative safety for the mother, but fetal mortality is consistently reported to be twenty percent [3]. Our understanding of placental hemodynamics during cardiopulmonary bypass remains limited, but experimental data suggests that there is a prostaglandin-mediated increase in placental vascular resistance that may lead to diminished placental blood flow [4]. It is believed that this reduction in placental blood flow is responsible for the decreased fetal survival associated with cardiopulmonary bypass [3]. Various adjunctive measures have been found experimentally to inhibit this prostaglandin mediated increase in placental resistance [3,4]. Some of these, such as maintenance of high perfusion pressure and flow rate, appear clinically to be effective in decreasing fetal mortality [3,4]. The use of pulsatile perfusion during extracorporeal circulation has been shown to attenuate this placental response in sheep [5]. We herein report a case where pulsatile cardiopulmonary bypass was successfully used for complex aortic valve and ascending aortic replacement, with both maternal and fetal survival.
A 25-year-old female, grava 6, para 3, presented in the 11th week of pregnancy with class III dyspnea on exertion. The patient had a history of rheumatic fever in childhood and a II/VI diastolic murmur. An echocardiogram showed a massively dilated aortic root with a diameter of 6.8 cm, moderate to severe aortic insufficiency, and mild left ventricular hypertrophy without dilation. After counseling the patient on the risk of pregnancy and delivery, as well as the risk of surgery, she refused a proposed abortion and elected to proceed with aortic valve and ascending aortic aneurysm replacement and to attempt to maintain the intrauterine pregnancy. Magnetic resonance imaging (MRI) was performed to avoid radiation exposure. There was fusiform dilatation of the ascending aorta to the level of the great vessels, the maximum diameter being 6.9 cm (Fig 1 ). Axial cine images using electrocardiographic gating were obtained showing 3+ aortic regurgitation, mild left ventricular dilatation, and reduced left ventricular contractility with an ejection fraction of 40%.
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Fig 1. Anterior-posterior (A) and lateral (B) projection of magnetic resonance imaging (MRI) study in the patient presented. Note the markedly dilated ascending aorta. Gated studies were also performed to delineate the degree of aortic insufficiency and left ventricular functional status as well as the status of the coronary arteries (not shown).
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Anesthesia was maintained with enflurane and pancuronium, and supplemented with fentanyl. Preoperatively methylprednisolone was given. Using right femoral artery and right atrial cannulation, pulsatile cardiopulmonary bypass was instituted using a Cobe-Stockard pulsatile pump (Cobe Cardiovascular, Arvada, CO) primed with lactated Ringer’s solution. Mean arterial pressure was 68 to 74 mm Hg during bypass and the pulse pressure was maintained at approximately 35 mm Hg. Mean flows were greater than 2.5 liters per minute per meter squared. Moderate systemic hypothermia to 32 degrees celsius was accomplished. Retrograde cold blood cardioplegia was used and the aortic valve was replaced with a 25 mm porcine bioprosthesis. The sinuses of Valsalva and coronary ostia were preserved, and the ascending aorta was replaced with a 30 mm Dacron graft. The patient was weaned from cardiopulmonary bypass without difficulty and the fetal heart rate was stable. Aortic cross clamp time was 53 minutes and cardiopulmonary bypass was 67 minutes. Her postoperative course was unremarkable and she was discharged to home on postoperative day (POD) 5 in stable condition. She subsequently delivered a healthy infant at 39 weeks gestation with Apgar scores of 9 at 1 and 5 minutes post delivery.
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Comment
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The incidence of cardiac disease in pregnancy is approximately two percent, with rheumatic disease accounting for the majority [1]. The physiologic changes of pregnancy may contribute to the worsening of valvular disease during the gestational period. In addition, hormonal and hemodynamic changes associated with pregnancy predispose the patient to aortic pathology such as dissection and aneurysmal dilatation [2]. When these processes lead to physiologic decompensation, maternal cardiac surgery is occasionally necessary. Although no large series has been published on cardiac surgery during pregnancy, cumulative reviews have shown a consistently low maternal mortality of approximately 3%, but a fetal mortality of approximately 20% [3].
Traditionally, high flow rates and high perfusion pressures have been recommended during cardiopulmonary bypass in pregnancy to preserve placental flow and thereby avoid hypotension-induced increased vascular resistance in the placenta [3]. This technique has been shown in experimental studies to improve placental perfusion and function during bypass in fetal lambs [4]. However, case reports have demonstrated fetal demise despite the use of high peak flow and pressure [3]. Theoretically, the maintenance of maternal pulsatile flow into the intervillous spaces of the uteroplacental vascular complex should maximize oxygen and nutrient transfer. Experimental data, again in fetal lamb preparations, have suggested that pulsatile flow may better preserve placental hemodynamic function and were the impetus for its use in this case [5,6 ]. A previous report on the use of pulsatile flow in a pregnant patient documented an intrauterine fetal demise, though in that instance the patient was in the third trimester with acute prosthetic endocarditis and thus represents a somewhat different clinical situation than the case presented here [7].
There is minimal data available on the effects of pulsatile bypass on maternal uteroplacental circulation. During normal pregnancy the uteroplacental arteries are maximally dilated, presumably as a result of localized production of prostacyclin [8]. Data from fetal lamb preparations have shown that nonpulsatile perfusion leads to a vasoconstrictive response of the fetal placental circulation [5]. This is believed to be mediated by prostaglandins and/or inhibition of tonic production of endothelium-derived relaxation factor nitric oxide (NO) [6, 9]. This increase in placental vascular resistance does not occur with pulsatile perfusion in the fetal lamb model. In addition, pulsatile perfusion has been shown in a clinical setting to reduce endogenous catecholamine production and peripheral vascular resistance during bypass [10]. Again theoretically, this data would seem to favor improved maintenance of maternal uteroplacental blood flow with pulsatile perfusion.
In conclusion, cardiac surgery during pregnancy is an infrequent but challenging problem. Based upon experimental evidence it appears that pulsatile perfusion may better maintain placental hemodynamics and thus hopefully lead to improved fetal outcome. We have reported the use of this technology with a successful outcome. Further data on the use of pulsatile perfusion in pregnancy is indicated.
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Acknowledgments
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The authors acknowledge the technical support of Mr Don Bicknell, CCP, in the preparation of this manuscript.
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References
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Blackburn S.T., Loper D.L. The placental period and placental physiology. In: Blackburn S.T., Loper D.L., eds. Maternal, fetal and neonatal physiology: a clinical perspective. Philadelphia, PA: W.B. Saunders, 1992:36-108.
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Abstract
Introduction
