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Ann Thorac Surg 2005;80:716-717
© 2005 The Society of Thoracic Surgeons

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Case report

Complete Atrioventricular Block Decreases Left Ventricular Assist Device Flow Rate

^a Cardiac Surgery Department, La Timone University, Marseille, France
^b The Ottawa Heart Institute, Ottawa, Ontario, Canada

Accepted for publication February 17, 2004.

^_* Address reprint requests to Dr Mesana, University of Ottawa Heart Institute, 40 Ruskin St, Room 340 2B, Ottawa, Ontario K1Y 4W7, Canada (Email: tmesana{at}ottawaheart.ca).

	Abstract

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A 52-year-old man, living at home, had been on left ventricular assistance for 15 months with a Novacor pump (Worldheart, Ottawa, ON, Canada). Following the onset of effort dyspnea that had recently become worse, he was admitted to the hospital. A review of the pump showed that its flow rate had significantly decreased. An electrocardiogram showed a third-degree atrioventricular block. A pacemaker was implanted and the patient became asymptomatic immediately afterwards. This clinical case report shows the importance of satisfactory right ventricle filling in these patients. Right ventricle filling can be impaired by conduction disorders.

	Introduction

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An implantable left ventricular assistance device is preferentially used for long-term support. The pump flow depends on a good right ventricular filling. We describe here an unusual cause of right ventricular filling impairment that was due to a complete atrioventricular block.

A 52-year-old man with terminal ischemic heart disease and a history of several attacks of myocardial infarction was admitted to the emergency department and sent to the intensive care unit in a state of severe cardiogenic shock. Despite inotropic life support, the patient’s hemodynamic condition became progressively worse and he developed oliguria.

Cardiac catheterization showed a cardiac index of 1.7l L·min^–1 ·m^–2), mean pulmonary wedge pressure, 25 mm Hg; central venous pressure, 14 mm Hg; and mean pulmonary arterial pressure, 44 mm Hg. In this emergency setting the patient was given left ventricular assistance with a Novacor (Worldheart, Ottawa, ON, Canada) implant.

Severe right ventricular failure developed in the patient the day after surgery, despite inotropic support and use of nitric oxide. The patient was given temporary right ventricular assistance with a Biomedicus (Medtronic, Minneapolis, MN) centrifugal pump. He was weaned off the pump 48 hours later. His electrocardiogram showed a regular sinusal rhythm with a first-degree atrioventricular heart block. He recovered sufficiently to be released from hospital and was sent home.

The patient was readmitted 15 months later following the onset of effort dyspnea, which progressively became worse. The initial clinical examination and the laboratory test results showed no anomaly. A review of the Novacor pump showed the flow rate had significantly decreased: 6 L/min for a normal flow of 7.2 L/min while resting, for a patient weighing 110 kg. An electrocardiogram showed a third-degree atrioventricular heart block with a ventricular escape rhythm of 20 pulsations per minute. Electrophysiologic exploration revealed an infra-Hisian block. A dual-chamber pacemaker (KAPPA D, Medtronic, Minneapolis, MN) was implanted, and the output from the left ventricular assist device immediately returned to its normal level. At this time, cardiac echocardiography showed a trivial tricuspid regurgitation and a systolic pulmonary artery pressure of 30 mm Hg.

The patient underwent heart transplantation 2 years later and is currently doing well.

	Comment

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The Novacor implantable left ventricular assist device is designed to work parallel to the left ventricle, providing it with electrical assistance. A cannula placed at the tip of the left ventricle aspirates the blood, which the pump then reinjects into the ascending aorta. [1]. The assisted flow-rate obviously correlates with the filling of the right ventricle.

Postoperative management of the right ventricle is important and can often be tricky. An increase in pulmonary resistance, the onset of rhythm disorders such as atrial fibrillation or ventricular tachycardia, or the onset of atrioventricular heart block can compromise right ventricular function. An increase in pulmonary resistance usually occurs immediately after surgery, long-term left ventricular unloading generally induces a significant decrease in pulmonary resistance. However, the onset of rhythm or conduction disorders can occur at any time and must be researched systematically if the assisted flow-rate decreases.

The placement of a permanent pacemaker has already been described in a patient previously implanted for left ventricular assistance [2], but in this case, the pacemaker was implanted immediately after surgery in an attempt to optimize the patient’s heart rate because of first-degree atrioventricular heart block leading to left ventricular failure. Our patient had a long-term implant and received a pacemaker for delayed atrioventricular heart block.

Some authors have shown that ventricular rhythm disorders are well tolerated in these patients [3], as the drop in pulmonary pressure permits passive filling of the right ventricle. This is why in some cases, serious rhythm or conduction disorders that are well tolerated only induce a moderate drop in the flow rate of the pump.

This clinical case report shows that an unexplained drop in the flow rate of a left ventricular assistance implant should systematically be explored to detect a potentially serious conduction disorder that can be corrected by the implantation of a pacemaker.

	References

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1. McCarthy PM, Portner PM, Tobler HG, et al. Clinical experience with the Novacor ventricular assist system J Thorac Cardiovasc Surg 1991;102:578-586.[Abstract]
2. Cave MH, Wallwork J, Schofield PM. Permanent pacing in a patient with a left ventricular assist system Heart 1996;75:525-527.[Abstract/Free Full Text]
3. Oz MC, Rose EA, Slater J, et al. Malignant ventricular arrhythmias are well tolerated in patients receiving long-term left ventricular assist devices J Am Coll Cardiol 1994;24:1688-1691.[Abstract]

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