January 1997
Cardiac risk of noncardiac surgery in patients with asymmetric septal hypertrophy.

Haering JM, Comunale ME, Parker RA, Lowenstein E. Douglas PS, Krumholz HM, Manning WJ. Anesthesiology 1996; 85:254-9

[ see abstract below ]

One of the most feared underlying medical conditions in the patient undergoing anesthesia is asymmetric septal hypertrophy (ASH), also referred to as subaortic stenosis or hypertrophic obstructive cardiomyopathy. Although it is a rare disorder (0.5% of patients with cardiac disease), these patients tolerate hypovolemia, hypotension and tachycardia extremely poorly. This reviewer has anecdotal experience of at least one intraoperative death which occurred when the anesthesia team failed to maintain intravascular volume and hematocrit in a young man with ASH undergoing back surgery.

In the August 1996 issue of Anesthesiology, Haering and colleagues review 77 cases in whom ASH was identified by echocardiogram prior to surgery. Haering et al. remind us that ASH is a variant that occurs in about a quarter of patients with hypertrophic cardiomyopathy, an inherited autosomal dominant disorder, characterized by dynamic left ventricular outflow tract (LVOT) obstruction. In their review, ASH was defined when the echocardiographic ratio of thickness of the septum to the posterior left ventricular wall exceeded 1.5. Thirty of the 77 patients had a high LVOT gradient (mean 31 +/-22 mmHg). Ten patients underwent spinal or epidural anesthesia.

Perioperative cardiac events were defined as major (death, life-threatening dysrhythmia, myocardial infarction) or minor (congestive heart failure, myocardial ischemia, dysrhythmias not requiring urgent treatment, transient hypotension). The overall incidence of adverse perioperative cardiac events was 40%. Although there were no deaths, one patient had a myocardial infarction and developed ventricular tachycardia requiring cardioversion. The remaining 30 patients had "minor" cardiac events.

Predictors of perioperative cardiac events included major surgery, intensity of monitoring, length of surgical procedure, and advanced age (in minor surgery). Interestingly, factors such as the severity of the LVOT gradient, mitral regurgitation and history of prior myocardial infarction were not statistically related to adverse cardiac events. There were no differences in outcome whether patients received a general or regional anesthetic.

The authors compare their study with one of the few done previously, published by Thompson et al. in 1985 (1). They observed that both demonstrated the rarity of perioperative death and myocardial infarction, but that the present series had a much higher incidence of congestive heart failure (which was defined as the radiographic presence of alveolar infiltrates or new rales on auscultation), perhaps reflecting overzealous efforts to maintain left ventricular preload. However, they refute the recommendation made by Thompson et al. that spinal or epidural anesthesia be avoided in ASH, and do not advise against their use "as long as hemodynamics are controlled".

The finding that the intensity of monitoring was a significant predictor of perioperative cardiac risk is especially interesting in the light of the current furor regarding the alleged increased mortality risk associated with the use of pulmonary artery catheters. However, there are insufficient data to draw conclusions from this study, and the authors suggest that it might reflect the anesthesiologist's ability to recognize high-risk patients preoperatively.

In conclusion, this survey emphasizes that anesthesia for ASH is frequently complicated by myocardial ischemia, transient hypotension, stable dysrhythmias and signs of congestive heart failure. Despite the fact that the severity of the disease is defined by the degree of septal hypertrophy and LVOT obstruction, these appear to be less important predictors of perioperative cardiac risk than the magnitude and duration of the surgical procedure, and the age of the patient. One question that remains is: does it matter how we manage these patients perioperatively? One assumes the answer is a resounding Yes! but unfortunately this retrospective study does not provide any guidance in this regard.

Reference:
(1) Thompson R, Liberthson R, Lowenstein E. Perioperative risk of noncardiac surgery in hypertrophic obstructive cardiomyopathy. JAMA 1985; 254:2419-21.

Return to the Current Literature Review Front Page, or read the abstract:

ABSTRACT