Anesthetic management of a patient with hypertrophic cardiomyopathy with atrial flutter posted for percutaneous nephrolithotomy.

Hypertrophic cardiomyopathy (HCM) is a most common genetic cardiovascular disorder, characterized by asymmetric hypertrophy of the interventricular septum that leads to intermittent obstruction of the left ventricular outflow tract (LVOT). Clinical presentation ranges from absence of symptoms to sudden death in the young and disability at any age. Although patients are asymptomatic in basal conditions, but anesthesia and surgical stress can lead to exacerbation of the LVOT obstruction and may complicate the perioperative course. Therefore, complete understanding of the pathophysiology and anesthetic implications is needed for the successful perioperative outcome. We describe the successful management of a case of HCM with atrial flutter posted for percutaneous nephrolithotomy.

INTRODUCTION

Hypertrophic cardiomyopathy (HCM) is a mutational genetic disorder of myocardium transmitted as an autosomal dominant trait. Clinical diagnosis of HCM is established with echocardiography showing left ventricular hypertrophy (LVH) typically asymmetric in distribution and associated with a nondilated chamber in the absence of other cardiac or systemic disease that can lead to hypertrophy.[1] Clinical presentation may vary from asymptomatic patient to sudden unexpected death due to cardiac dysrhythmia during any phase of life.[2] The challenges for anesthesiologists in these patients are the high incidence of intraoperative left ventricular outflow tract (LVOT) obstruction, diastolic dysfunction, myocardial ischemia and atrial fibrillation or flutter.[3]

CASE REPORT

A 46-year-old male, weighing 60 kg diagnosed as bilateral renal calculi was posted for right percutaneous nephrolithotomy. Patient's history revealed episodes of palpitations, chest pain and syncope 5 years back. He was diagnosed then as HCM, and he was put on medical management (metoprolol, diltiazem) for the same. For last 6 months, patient was on anticoagulants (warfarin) due to new development of atrial flutter, since then he was symptomatically better but had fatigue, episodes of palpitations, dyspnea and angina on exertion.

On examination, pulse rate was 76 beat/min and blood pressure (BP) was 130/76 mmHg. Airway and systemic examination was normal except harsh systolic murmur at the apex. Laboratory investigations were normal except serum creatinine 1.73 mg/dl and international normalized ratio 2.5. Electrocardiogram (ECG) showed LVH and atrial flutter with controlled ventricular rate. Holter study was done which was showing heart rate varying from 50 to 132 beat/min and occasional ventricular premature contractions. Transthoracic echocardiography showed LVH, asymmetric interventricular septal hypertrophy 23 mm, posterior wall thickness 14 mm (Thickness ratio 1:1.6), left ventricular ejection fraction 50%, regional wall motion abnormality, no LVOT, moderate mitral regurgitation (MR), and mild tricuspid regurgitation with moderate pulmonary arterial hypertension (PAH). There was no clot formation.

All the cardiac medications were continued till the day of surgery. Warfarin was stopped 5 days before surgery and bridged with low molecular weight heparin, last dose of which was given 12 h prior to surgery. In the operation theater, monitoring was instituted with pulse oximetry, ECG with automated ST segment analysis, arterial line for invasive BP and central venous pressure through right internal jugular vein. Prophylactic antibiotic was given 30 min before induction. Patient was preloaded with 500 ml normal saline and premedicated with fentanyl 3 μg/kg body weight and midazolam 1 mg. General anesthesia was induced with thiopentone sodium 5 mg/kg body weight, and vecuronium 0.1 mg/kg body weight was used to facilitate endotracheal intubation. Lignocaine 60 mg intravenous was given to attenuate laryngoscopy stress response. Anesthesia was maintained with 50% nitrous oxide in oxygen, isoflurane 0.4–1% and vecuronium bolus with intermittent positive pressure ventilation. As the surgery was in the prone position, proper precautions were taken to rapidly turn the patient to supine position if required. External defibrillator pads were applied before turning the patient prone, and all resuscitation and antiarrhythmic drugs were kept ready to tackle an inadvertent arrhythmic event.

The hemodynamic parameters were monitored which remained stable throughout the procedure with heart rate from 64 to 84 beat/min and systolic BP from 100 to 140 mmHg. The procedure lasted for 1½ h, during which 1.5 L normal saline was given. Urine output could not be measured in this patient.

At the end of the surgery, neuromuscular block was reversed with standard doses of neostigmine and glycopyrrolate and the trachea was extubated. The patient was observed overnight in postanesthesia care unit and discharged on the 3rd postoperative day.

DISCUSSION

Hypertrophic cardiomyopathy is a complex condition, the pathophysiologic determinants of clinical course and disease progression in HCM include dynamic obstruction to LV outflow, diastolic dysfunction, impaired coronary vasodilator reserve, myocardial ischemia, and supraventricular or ventricular tachyarrhythmias.[3] The symptoms include dyspnea with exertion, angina and dizziness varying from light headedness, presyncope, syncope and sudden death.[4] Paroxysmal or chronic atrial fibrillation or flutter complicates the course of a substantial minority of patients with HCM and adds new or worsens the existing symptoms and affects the course of the disease.[45] Such patients should receive atrial antiarrhythmic agents and warfarin if not contraindicated.

Medical therapy of HCM consists of beta blockers and calcium channel blockers. Disopyramide may benefit in patients of hypertrophic obstructive cardiomyopathy with atrial fibrillation. The rationale for using beta blocker is their ability for negative inotropism. Beta blocker prolongs diastolic filling time by decreasing heart rate, decreases myocardial oxygen requirement (increase in left ventricular end-diastolic volume and a resultant decrease in LVOT gradient) and improves exercise tolerance. Diltiazem provides benefits due to ventricular relaxation and filling in addition to control of ventricular rate it also shortens intraventricular relaxation time and enhances early diastolic filling in patients with HCM. Atrial fibrillation and flutter are the most common dysrhythmias in patients with HCM and are associated with increased risk of thromboembolism that mandates institution of anticoagulants.[678] Our patient was being treated with metoprolol, diltiazem, and warfarin.

Goal of anesthetic of management in a patient with HCM for noncardiac surgery is to prevent occurrence of LVOT obstruction, arrhythmias and diastolic dysfunction. Strategies to establish this are:[39]

Maintenance of sinus rhythm

Reduction in sympathetic activity to reduce chronotropy and inotropy

Maintenance of left ventricular filling

Maintenance of systemic vascular resistance.

The concerns pertaining to our patient were the presence of HCM albeit without LVOT, presence of MR, PAH, symptoms of palpitations, syncope on exertion, atrial flutter and conduction of surgery in the prone position thus precluding access to the precordium.

Although a patient with HCM may not demonstrate LVOT under basal conditions, its occurrence on provocation has been described. Poliac et al.,[3] have reported that patients without signs of LVOT obstruction at rest preoperatively should not be regarded as free from the possibility of developing dynamic obstruction with the administration of anesthetic agents. Steps to prevent the conditions that increases myocardial contractility (e.g., tachycardia, stress) or decreases preload and ventricular volume (e.g., vasodilators, hypovolemia, hypotension) must be taken, as the LVOT gradient increases with volume depletion.[4] Maintenance of sinus rhythm is crucial in these patients because of the dependence of preload on atrial contraction.

Premedication has the important role in reducing sympathetic activity and therefore reducing cardiac workload. Preloading before induction helps to maintain stroke volume and possibly minimizing adverse events of positive pressure ventilation and cardio depressant actions of induction agents. Invasive monitoring for BP and LV filling pressures should be done in HCM patients undergoing noncardiac surgery, as we did in our case.

One must be Vigilant especially during induction, laryngoscopy, intubation, positioning, extubation and for possible blood loss to prevent catecholamine surge that may result in arrhythmias, LVOT obstruction, and increased myocardial oxygen demand. Attempts to prevent tachycardia, hypotension, sympathetic stimulation, increased myocardial contractility and decrease in preload and afterload are of paramount importance.[101112] We studied few case reports of similar cases and summarizes their case management in brief in Table 1.

Table 1

Summary of anesthetic management described in previously published case reports

CONCLUSION

Hypertrophic cardiomyopathy is a common cause of sudden cardiac death at any age. The combined stress of anesthesia and surgery may result in potential complications during the procedure in these patients. Skilled perioperative care and prevention of complications by intraoperative vigilance and careful hemodynamic monitoring is of prime importance in a patient of HCM for noncardiac surgery.