Baby Memorial Hospital, Kozhikode, Kerala, India. PIN: 673004
Address for
Correspondence: Dr. MC Rajesh DA, MD, MBA, Senior
Consultant Anaesthesiologist, Baby Memorial Hospital,
Kozhikode, Kerala, India. PIN: 673004. E- mail:
rithraj2@yahoo.co.in
Keywords: Hypertrophic Obstructive Cardiomyopathy,
HOCM, anaesthesia
In order to have an uneventful peri-operative period it is
imperative for anaesthesiologist to maintain patients in
perfect haemodynamics. But patient's underlying cardiac
status has lot to do with the patient's peri-operative
course. Hypertrophic obstructive cardiomyopathy (HOCM) is
one such condition which is relatively common with an
incidence of 1 in 500 [1]. In order to safely cruise
patients during anaesthesia, it is important for
anaesthesiologists to have a basic understanding of the
pathophysiology, haemodynamic changes and anaesthetic
implications of disease. If adequate anticipation and
peri-operative care are not taken, anaesthesia and surgery
can complicate the peri-operative outcome [2].
Intraoperative factors like increase in myocardial
contractility, tachycardia, hypotension or vasodilation can
precipitate an exacerbation of the obstruction [2].
HOCM is a genetically inherited condition with basic
histological change as abnormal myocytes. There is unusual
myocardial hypertrophy developing without pressure or volume
overload [3]. In the initial stages of disease, hypertrophy
may be confined to septum. But as the disease advances, it
can extend to the free wall of the left ventricle, and
finally can result in concentric hypertrophy of left
ventricle. This can result in a pressure gradient between
apical left ventricular chamber (LV) and left ventricular
outflow tract (LVOT). LVOT obstruction thus created can
result in an increase of LV pressure further leading to
hypertrophy, reduced compliance and worsening LVOT
obstruction [4]. Twenty to thirty percent of hypertrophic
cardiomyopathy patients develop significant septal
hypertrophy that can even obstruct the aortic outflow,
resulting in sudden unexplained death [5]. Systolic anterior
motion of mitral valve can lead to mitral regurgitation [6].
Stiff and hypertrophied ventricle with impaired compliance
results in diastolic dysfunction [6].
Pre-operative echocardiogram is important to reveal left
ventricular function. This could be normal to supranormal
with high ejection fraction [7]. Abnormalities of
ventricular relaxation, rhythm disturbances, diastolic
dysfunction, moderate mitral regurgitation and septal motion
abnormalities are all reflected on the echocardiogram [8].
Electrocardiographic (ECG) abnormalities noted are increased
precordial voltage and non specific ST-T changes [9].
Asymmetrical septal hypertrophy produces deep narrow Q waves
in lateral and leads. This can be confused with ECG finding
in myocardial infarction. Left ventricular diastolic
dysfunction may result in compensatory left atrial
hypertrophy, with signs of left atrial enlargement. Atrial
fibrillation, ventricular dysrhythmias and supraventricular
Medical management of HOCM includes treatment with beta
adrenergic receptor antagonists, which should be continued
in the peri-operative period [10]. Many of the symptomatic
patients for surgery come with an Automatic implantable
cardioverter defibrillator (AICD) in situ. In fact AICD has
become more popular and the equipment has evolved over a
time to be very sophisticated. Understanding the functions
of the device is essential for optimal care of the patient
and equipment. Septal ablation with ethanol is a relatively
new modality and successful ablation can result in immediate
decline of LVOT gradient [11].
Intraoperative monitoring include pulse oximetry, ECG, non
invasive BP, invasive BP, automated ST segment analysis,
central venous pressure (CVP), end-tidal carbon dioxide
(ETCO2), temperature and urine output monitoring. Use of
trans-oesophageal echocardiogram is strongly advocated.
The goal of anaesthesia is to ensure adequate ventricular
filling with slow heart rate and modest expansion of
intravascular volume [12]. Factors which can exacerbate the
outflow tract obstruction like increase in myocardial
contractility or a decrease in systemic vascular resistance
has to be avoided meticulously [12]. So while anaesthetizing
these patients, considerations should be given to maintain
adequate intravascular volume and venous return,
maintain systemic vascular resistance, slow heart
rate, with sinus rhythm and aggressively treat atrial
fibrillation and other tachyarrhythmias [12]. Due attention
should be paid to post-op analgesia, since it can result in
cathacholamine release and development of tachyarrythmias.
Any potential sympathetic response should be minimized
during the course of anaesthesia. Patients with HOCM are at
risk for peri-operative development of of arrhythmias and
development of ventricular arrhythmias is very common [13].
Routine infective endocarditis prophylaxis is no longer
recommended [14]. Because of potential peripheral
vasodilation, regional anaesthesia is better avoided [15].
But there are reports in literature, of caesarean delivery
being successfully undertaken with regional anaesthesia [12,
16].
Managing a victim of cardiac arrest in HOCM is different and
the pathophysiology of disease has to be kept in mind. Use
of ionotropic agents is contraindicated if there is left
ventricular outflow obsrtruction, as it can worsen the
situation. Alpha agonists, IV fluids and rapid correction of
arrhythmias are more justified in this situation. In fact,
application of external defibrillator pads before inducing
the patient is highly recommended [17].
Conclusion
The management HOCM includes through understanding of the
pathophysiological process of disease. It is imperative to
maintain specific haemodynamic goals to prevent the
intraoperative complications associated with it.
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