|Year : 2007 | Volume
| Issue : 2 | Page : 134
Anaesthesia management of a patient with hypertrophic obstructive cardiomyopathy undergoing Morrow's septal myectomy
Naresh Kumar Agarwal1, Poonam Malhotra Kapoor2, Shiv Chaudhary3, Usha Kiran4
1 Senior Resident, Department of Cardio thoracic surgery, AIIMS, India
2 Assoc. Prof., Department of Cardio thoracic surgery, AIIMS, India
3 Additional Prof., Department of Cardio thoracic surgery. AIIMS, India
4 Prof. & Head. Department of Cardiac Anaesthesia, AIIMS, India
|Date of Acceptance||02-Mar-2007|
|Date of Web Publication||20-Mar-2010|
Poonam Malhotra Kapoor
CNC, AIIMS, New Delhi
Source of Support: None, Conflict of Interest: None
Hypertrophic obstructive cardiomyopathy (HOCM) is a rare disorder. There is paucity of literature on anaesthetic management of this disorder. Aim of this case report is to highlight the anaesthetic problems encountered during management of such patients.
A thirty-five year old male was admitted with atypical chest pain for last one year. X-ray chest revealed cardiomegaly (CT ratio 0.6). Electrocardiographic findings were left axis deviation with left ventricular hypertrophy. On echocardiography, there was moderate mitral regurgitation (MR), systolic anterior motion (SAM) of anterior mitral leaflet and prominent systolic narrowing of left ventricle cavity. Transoesophageal echocardiography (TOE) also showed an anomalous muscle bundle stretching into LV causing obstruction. Preload was kept high. Systemic vascular resistance (SVR) was maintained, avoiding use of vasodilators and inotropes. Morrow's septal myectomy was done. Anomalous muscle bundle was excised. On postoperative TOE, there was no MR and no obstruction.
Optimal anaesthetic management in such patients involves maintaining adequate preload, systemic vascular resistance and minimal outflow obstruction. Other considerations are to maintain haemodynamic stability, sinus rhythm and afterload. Transoesophageal echocardiography is an extremely useful monitoring device in such patients.
Keywords: Hypertrophic obstructive cardiomyopathy; transoesophageal echocardiography; septal myectomy
|How to cite this article:|
Agarwal NK, Kapoor PM, Chaudhary S, Kiran U. Anaesthesia management of a patient with hypertrophic obstructive cardiomyopathy undergoing Morrow's septal myectomy. Indian J Anaesth 2007;51:134
|How to cite this URL:|
Agarwal NK, Kapoor PM, Chaudhary S, Kiran U. Anaesthesia management of a patient with hypertrophic obstructive cardiomyopathy undergoing Morrow's septal myectomy. Indian J Anaesth [serial online] 2007 [cited 2020 Mar 28];51:134. Available from: http://www.ijaweb.org/text.asp?2007/51/2/134/61129
| Introduction|| |
Hypertrophic obstructive cardiomyopathy (HOCM) is a rare disorder that involves hypertrophy of the left and/ or right ventricle and may be classified as symmetric or asymmetric, obstructive or non-obstructive. Subaortic hypertrophic obstructive cardiomyopathy (HOCM) is most common.  It is characterized by asymmetric hypertrophy of the interventricular septum, resulting in dynamic obstruction of the left ventricle outflow tract (LVOT). Rarely, right ventricle may be involved. The extent and site of the hypertrophy can vary greatly and significantly influences the manifestations of the disease.  It is an autosomal disorder with a high degree of penetrance with male:female ratio of 2:1.  Average mortality, with medical treatment is approximately 3-4% per year.  Management of this condition involves medical, electrophysiological, percutaneous transluminal septal myocardial ablation and surgical therapy. ,, This is a rare disorder extremely challenging to anaesthesiologist. Because of paucity in literature, we describe the anaesthetic management of one such patient undergoing surgical myectomy with emphasis on role of TOE in perioperative management.
| Case report|| |
A thirty-five year old male was admitted with intermittent atypical chest pain for last one year. The pain increased after walking and taking meals (NYHA class III) without any radiation of pain. Patient was not on any medical therapy. On physical examination, pulse rate was 88 beats per minute, blood pressure of 120/70 mmHg. There was grade 3/6 systolic murmur with increase in murmur with standing and valsalva maneuver. There was no family history of cardiac illness or sudden death. Chest roentgenogram showed cardiomegaly with cardiothoracic ratio of 0.6 with small aorta. There was left axis deviation with left ventricular hypertrophy (LVH) without any ST/T changes on electrocardiogram. Echocardiography revealed moderate MR, SAM of anterior mitral valve leaflet, severe left ventricular hypertrophy, asymmetrical septal hypertrophy and prominent systolic narrowing of left ventricle (LV) cavity without any regional wall motion abnormality (RWMA). Preoperative coronary angiogram was normal. Patient was diagnosed with hypertrophic obstructive cardiomyopathy. Patient opted for surgical septal myectomy.
Patient was premedicated with morphine (0.15 mgkg-1) and promethazine (0.5 mgkg-1) intramuscularly, 45 minutes before operation. Induction was done with slow intravenous (I.V.) incremental dose of injection thiopentone (3 mgkg-1) and injection fentanyl (5μgkg-1). Tracheal intubation was facilitated with injection rocuronium (1mgkg-1). A TOE probe (Hewlett Packard T 6210, Philips Sonos 5500) was inserted after induction of anaesthesia. Monitoring included five lead ECG, pulse oximetry, temperature, end-tidal carbon-dioxide (EtCO2), central venous pressure CVP), intraarterial blood pressure and TOE probe. Preoperative TOE showed moderate MR, SAM of anterior mitral valve leaflet and systolic narrowing of LV cavity without any RWMA. An anomalous muscle bundle stretching into LV causing outflow obstruction was present. Anaesthesia was maintained with inj rocuronium, oxygen and air. Halothane was used in low concentration (0.5-0.75 MAC). Haemodynamics were maintained to keep heart rate between 70-90 beats per minute, mean blood pressure of 60-70 mmHg. EtCO2 was maintained between 35-40 mm Hg and CVP was kept high (7-8 cm H2O) in the pre and post bypass period. Any episode of mean blood pressure <50 mm Hg was treated with 2-4 μg of norepinephrine and heart rate more than 100 beats per minute with esmolol (1 mg bolus). Myocardial depressants like benzodiazepines and vasodilators like nitroglycerin were avoided in the perioperative period. Heparin (4 mgkg-1) was administered before onset of cardiopulmonary bypass (CPB) to achieve activated coagulation time (ACT) of 480 sec. Aorto-bicaval cannulation was done. On CPB, mean arterial pressure of 50 mm Hg, pump flow (2.2-2.4 L/min/m2), alpha stat pH management and temperature of 32 °C was maintained. Septal myectomy (Morrow's procedure) was done under hypothermic CPB. Anomalous muscle bundle causing LVOT was excised. Patient was weaned off cardiopulmonary bypass on minimal dose of inj. dobutamine (5 μgkg-1min-1) keeping CVP of 7-8 cm H2O. Protamine (1.3 × heparin dose) was used to reverse the effect of heparin, after reversal ACT was 120 sec. After repair, there was trivial mitral regurgitation and no outflow gradient on TOE. Contractility of the heart improved after repair. Patient was extubated on first postoperative day and discharged on sixth postoperative day. Post-operative course remained uneventful.
| Discussion|| |
There are few case reports published about anaesthetic management of HOCM in literature. Subaortic HOCM is, characterized by systolic dysfunction and the presence of an intraventricular pressure gradient that may be persistent, labile or latent. There may be diastolic dysfunction with abnormalities of ventricular relaxation which may be complicated by rhythm disturbances.  LV systolic function in patients with HOCM are usually normal to supranormal with a high ejection fraction.  Systolic function is affected by an increase in the intraventicular gradient. Diastolic dysfunction in patients with HOCM is caused by decreased ventricular compliance and impaired ventricular relaxation.  Patients may have systolic anterior motion of the anterior mitral valve leaflet that results in MR resulting in left atrial enlargement, predisposing to atrial fibrillation. The perioperative management of patients with HOCM is challenging. Management of this condition can be medical, electrophysiological or surgical.  Negative inotropic drugs like beta blockers and calcium channel blockers are used to decrease the degree of outflow tract obstruction.  Dual chamber pacing has been recognized for its ability to decrease the subaortic pressure gradient.  Percutaneous transluminal septal myocardial ablation, in which absolute alcohol (2-5 ml), is injected in one or more septal branches of the left anterior descending coronary artery may reduce symptoms and improve exercise tolerance however, it carries the risk of heart block.  These therapeutic approaches have reduced the number of patients undergoing surgical procedures. Surgical myotomy or myectomy is performed for symptomatic HOCM that is unresponsive to medical therapy. Myectomy results in significant symptomatic improvement by septal thinning, widening of LV outflow tract and resolution of SAM. Aims of anaesthetic management undergoing surgical management of such patients are to maintain normal sinus rhythm, adequate preload and alterload and to minimize or prevent outflow obstruction.
Anaesthetic technique and the perioperative management of these patients must aim to maintain haemodynamic stability, maintaining adequate preload and afterload. Avoiding vasodilators and avoiding agents that increase contractility are pivotal in the management of these patients. Intra-operative goals include maintaining sinus rhythm, minimum stressful stimuli and minimize or prevent dynamic LV outflow tract obstruction.
This patient was adequately premedicated to reduce perioperative anxiety. Such patients should be given adequate premedication, to reduce stress response (like benzodiazepines, opioids). Anaesthesia was induced with low doses of thiopentone and fentanyl. Rapid inj of such drugs can lead to hypotension and tachycardia which are not desirable in such patients. Rocuronium was used for intubation because it causes minimal increase in heart rate. Vecuronium is other muscle relaxant that can be used as it decreases heart rate and thus avoids LV outflow tract obstruction. Volatile anaesthetic like halothane is beneficial for anaesthesia maintenance because it decreases both contractility and heart rate and awareness. Halothane in comparison to isoflurane has least effect on systemic vascular resistance and decreases heart rate and causes slight myocardial depression, all of these properties are beneficial for such patients. We used low doses of opioids to suppress catecholamine release and ensure haemodynamic stability as high doses of opioids can lead to prolonged respiratory depression. , Episodes of hypotension can be treated with trendelenburg position, volume replacement and/or vasoconstrictors like norepinephrine or phenylephrine. Dobutamine was used in minimal dose under-TOE monitoring after relieving obstruction during weaning. Dobutamine should be used cautiously in preoperative period as it can cause tachycardia and decrease in afterload, aggravating the obstruction. b-receptor antagonists, in contrast, decrease the pressure gradient and improve cardiac output by decreasing outflow obstruction. Episodes of tachycardia in the perioperative period may be treated with b-receptor antagonist like esmolol.
Adequate preload should be the goal.  We used CVP and TOE monitoring in this case. CVP should be kept high as adequate preload is necessary to maintain optimal cardiac output and avoid any undue increase in contractility because of hypovolemia. TOE helps to assess filling conditions. A pulmonary artery catheter may be desirable in patients to optimize filling conditions particularly in patients with compromised myocardial function but carries the risk of arrhythmia and adds cost to patient.
Intra-operative TOE has become an integral part of surgical myectomy. TOE helps in detection of previously unsuspected structural abnormalities and the assessment of procedural results and potential complications.  TOE monitoring helps in assessing degree of MR, extent and gradient of obstruction. TOE also helps in assessing volume status of patients. TOE according to us, is must for such cases. We assessed degree of obstruction, severity of MR, RWMA and preload status pre-operatively and postoperatively.
There was no rhythm problem in our case but arrhythmias may be problematic in such patients. Atrial fibrillation and junctional rhythm are poorly tolerated in HOCM patients due to the loss of atrial kick. Arrhythmias, particularly atrial fibrillation require prompt treatment.  Beta blockers and amiodarone are drugs to control arrhythmias. Digoxin is unsuitable because of its positive inotropic effects. Calcium channel blockers should be used with caution because of the potential for systemic vasodilation. b-blockers like esmolol are helpfu1. 
| Conclusions|| |
Optimal anaesthetic management in patients with HOCM involves maintaining adequate preload, optimal systemic vascular resistance and minimal outflow obstruction. TOE monitoring in preoperative, intraoperative and postoperative period is an extremely useful adjunct in the successful management of such patients undergoing Morrow's septal myectomy.
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