Ann Thorac Surg 1996;61:1086
© 1996 The Society of Thoracic Surgeons
Invited Commentary
Invited Commentary
Alex G. Little, MD
Department of Surgery, University of Nevada School of Medicine, 2040 W Charleston Blvd, #601, Las Vegas, NV 89102.
See also page="1083.
Concern about cardiac dysrhythmias was a prominent issue during the early years of thoracic surgery. This ranged from the ``knowledge'' at the turn of the century that operative stimulation of the vagus nerve would lead to instant cardiac cessation and death to more appropriate and less dramatic concerns about postoperative dysrhythmias after major lung resection. Since the first actual documentation of cardiac dysrhythmias after pulmonary resection in the early 1940s, there has been considerable interest in their incidence and nature, their predictability from preoperative assessment, the ability to prevent their development, and their treatment. Most dysrhythmias are supraventricular and occur after major lung resection, and by far the most common is atrial fibrillation. The incidence has been documented to range between 3% to 20% after lobectomy and up to 40% after pneumonectomy. The two most germane observations are that dysrhythmias are more common in older than younger patients and that they are associated with an increased perioperative mortality, especially after pneumonectomy.
Because of these last two observations, interest in prophylaxis against postoperative dysrhythmias has been considerable. For many years preoperative digitalization of older patients, particularly those planned for pneumonectomy, was standard. Recent experience, however, suggests that preoperative digitalization is not beneficial and may even be associated with its own complications. With appropriately increasing confidence in intensive care monitoring and therapy, prophylactic digitalization is no longer standard. However, it still remains true that the development of atrial dysrhythmias after lung resection is associated with an increased risk of postoperative death. Consequently, evidence that effective, safe prophylactic therapy existed would be welcomed. For that reason, the foregoing article is of interest. My own interpretation is that Van Mieghem and associates underestimate the clinical significance of their findings, and I think their report points the way to more appropriate investigations as to the role of verapamil. Verapamil is a slow calcium-channel blocker and, therefore, affects the slow depolarization activity, which is more important in sinoatrial and atrioventricular nodal tissue than Purkinje or muscle fibers. This slows conduction and prolongs refractiveness, which makes it effective against atrial arrhythmias. Van Mieghem and associates have shown a nearly 50% decrease (15% versus 8%) in arrhythmias in patients undergoing lung resection and receiving prophylactic verapamil. Even though this decrease in incidence was not found to be statistically significant, it seems obvious that there is a high likelihood of a beta statistical error. With a larger population of patients, a 50% decrease in the incidence of arrhythmias would have to be statistically significant. Further, one would imagine even more dramatic benefit without the associated hypotension or bradycardia that developed in some patients and led to interruption of verapamil administration. These side effects had no deleterious impact on patient outcome and, therefore, would not have to be considered as strong contraindications to prophylactic verapamil administration.
We know that the incidence of postoperative arrhythmias peaks on the second postoperative day, as confirmed by Van Mieghem and associates. Accordingly, the aggressive early loading schedule they used could probably be avoided. A more reasonable approach would be to begin an infusion at their described rate in the intensive care unit after arrival from the operating room, omitting a loading dose. Presumably the incidence of bradycardia or hypotension would be less but significant verapamil serum levels would be present by day 1 and 2 postoperatively when the risk of arrhythmia development is greatest. Accordingly, I would suggest that their findings are more significant than they themselves concluded, and this could be demonstrated with a modified dosage protocol. Given the important negative impact of an atrial dysrhythmia on an elderly patient recovering from a major lung resection, continued interest in the role of verapamil for prophylaxis against supraventricular dysrhythmias seems warranted.
