Intraoperative management of atrial fibrillation in a patient with restrictive cardiomyopathy.

A 65-year-old patient with renal amyloidosis presented for Trans Urethral Resection of Prostate (TURP). There were no symptoms pertaining to the cardiorespiratory system. Preoperative investigations showed only secondary cardiomyopathy. Intraoperatively the patient developed atrial fibrillation with hypotension which was successfully managed by cardioversion.

INTRODUCTION

American Heart Association classified cardiomyopathy into two major groups, primary and secondary.[1] Primary cardiomyopathy can be genetic, acquired or mixed. In secondary cardiomyopathy there is involvement of heart in the context of a multiorgan disorder. One important cause for secondary cardiomyopathy is amyloidosis. Disease has a restrictive physiology. Sudden cardiac death (SCD) is a recognized complication of cardiomyopathy.[234] Rarely the patient can present with a surgical problem with occult cardiac involvement which can be catastrophic intraoperatively. There are no reports in the literature of management of atrial fibrillation in a restrictive cardiomyopathy patient undergoing trans-urethral resection of prostate.

CASE REPORT

A 65-year-old male patient weighing 60 kg presented to our hospital with difficulty in passing urine since 3 months. He was diagnosed to be a case of benign prostatic hypertrophy (BPH) and was scheduled for trans-urethral resection of prostate (TURP). Previous medical records were incomplete except for an old diagnosis of renal amyloidosis. Presently he was asymptomatic and had a good functional status.

Preanesthetic checkup showed stable vital signs. Cardiovascular examination revealed a systolic murmur heard over apex. No raised jugular venous pressure or parasternal heave was present. Laboratory investigations were normal except for mild proteinuria. On electrocardiogram borderline left ventricular hypertrophy and left bundle branch block was present. Ultrasound examination of kidney showed no abnormality and prostrate volume amounted to 68 ml. 2D echocardiogram findings showed an ejection fraction of 55%, right ventricular systolic pressure (RVSP) 48 mmHg, left ventricular septum thickened 1.8 cm (normal 0.6-1.0 cm), concentric LVH, speckled appearance of myocardium, restrictive filling pattern of mitral inflow, dilated left atrium, moderate pulmonary artery hypertension, moderate mitral regurgitation and tricuspid regurgitation, normal left ventricular function and trivial pericardial effusion.

After obtaining consent for surgery and anesthesia, the patient was shifted to the operating room. Baseline monitoring was established. Intravenous (IV) access was done with 18G cannula. Left radial artery was cannulated with 20G cannula and heplocked. Spinal anesthesia was administered using 23G Quincke type spinal needle after positioning the patient in left lateral position. Combination of 1.2 ml 0.5% heavy bupivacaine and buprenorphine 30 μg was used to achieve a block level of T10 dermatome and the resection was started.

About 50 minutes through surgery, the ECG monitor showed a varying R--R interval with high heart rate of 128/min, with a fall in blood pressure to 80/40 mmHg. The patient remained conscious and alert. Pulse apex deficit was checked which was 18 and a diagnosis of atrial fibrillation with hypotension was made. Surgeon was requested to stop the resection. Combination of Etomidate 6 mg and Midazolam 1 mg was given slow IV for sedation. Oxygen was administered by face mask and a decision to cardiovert the heart was taken in view of hypotension with high ventricular rate. Using a biphasic defibrillator with an energy of 100 J cardioversion was attempted. The patient reverted back to normal sinus rhythm after a single shock. Postshock, the heart rate returned to 84/min and blood pressure to 118/78 mmHg. Surgical hemostasis was achieved and the patient was shifted to high dependence unit where he had an uneventful stay.

DISCUSSION

Amyloidosis is caused by the extracellular deposition of insoluble polymeric protein fibrils in tissues and organs. Diagnosis rests upon tissue biopsy, that after Congo red staining shows “apple-green birefringence” on polarization microscopy.[5] Organs involved are heart, liver, kidney, autonomic nervous system, and skin.[67] In primary systemic amyloidosis, kidneys are the most frequently affected organ. Next commonly involved organ is the heart, causing restrictive cardiomyopathy. Cardiomyopathy is a disease of heart muscle. In restrictive cardiomyopathy there is restrictive filling of the ventricles. There can be myocardial hypertrophy and diastolic dysfunction. Cardiac output is usually low and maintained by increased filling pressures and higher rate. Hypertrophied myocardium exhibits prolonged relaxation time and decreased compliance. Amyloid fibrils infiltrate the myocardium, especially around the conduction system and coronary arteries. Atrial dysrhythmias are common in amyloidotic cardiomyopathy because of dilated atrium and disorganized cellular architecture.

A challenging task in the preoperative evaluation is in whom the diagnosis has not yet been made. A subset of patients appear healthy under normal living conditions and are asymptomatic. Disease may be unmasked by stress of surgery and anesthesia. Our patient presented to the urology department with history of renal amylodosis, symptoms of obstructive uropathy, and occult restrictive cardiomyopathy. Cardiomyopathy is one of the important causes of sudden death under anesthesia.

Spinal anesthesia is regarded as the technique of choice for TURP. It offers many advantages over general anesthesia.[8] In patients with restrictive cardiomyopathy general anesthesia is often selected in preference to central neuraxial block because the sympathetic block produced by regional anesthesia can lead to significant hypotension. For procedures below umbilicus with a level of block of T10 dermatome, general or regional anesthesia can be selected as long as hemodynamic goals are met. Goals are directed mainly toward minimizing further decrease in cardiac output, systemic vascular resistance, and maintaining sinus rhythm. Preload must be kept high enough to support LV filling, but pulmonary edema must also be avoided. Even though central venous pressure monitoring with epidural anesthesia would have been ideal in this case, considering the good functional status of the patient, fairly normal LV function in echocardiography and easy access to central venous cannulation any time during surgery, we deferred instituting CVP monitoring. The presence of small prostate gland requiring short duration of resection and need for low block height, spinal anesthesia was planned keeping hemodynamic goals in consideration.

Hypotension as a response to spinal anesthesia in a patient having restrictive cardiomyopathy should be treated with a vasopressor and not by aggressive fluid replacement as it can result in pulmonary edema or TURP syndrome. Maintaining sinus rhythm is important as “atrial kick” is necessary for adequately preloading the ventricle. Unstable arrhythmias should be cardioverted immediately. Amiodarone has been successfully used for atrial and ventricular dysrhythmias at a lower dose. β-blockers, calcium channel blockers and digitals are relatively contraindicated as they interact with amyloid fibrils and produce heart block.[5] Recommended energy for narrow complex tachycardia with a biphasic defibrillator is 120-200J.[8] Single shock converted irregular rhythm into sinus rhythm.

In a patient with renal amylodosis, it is wise to rule out cardiac involvement before any anesthetic procedure. Amyloid cardiomyopathy is one of the important causes of sudden cardiac death under anesthesia. General or regional anesthesia can be selected as long as hemodynamic goals are met.