CARDIOLOGY
Anaesthesia
in Patients Suffering a Heart Murmur
Article review by Dr Lynette Bester
Dr Roxanne Buck Dr Gareth Zeiler
BSc BVSc
BVSc(Hons) MMedVet
(Anaes) DipECVAA
Onderstepoort Veterinary Academic Hospital, Section of Veterinary Anaesthesiology, Department of Companion Animals Clinical Studies, Faculty of Veterinary Science, University of Pretoria [email protected][email protected]
Heart murmurs diagnosed on precordial auscultation are a significant finding that warrant further
clinical investigation.
The clinical implications of the murmur requires
consideration to determine the anaesthetic risk.2 Patient signalment, presenting complaint, presence of
concurrent diseases, exercise tolerance and current
medication are important considerations to address
during a pre-anaesthetic evaluation. A heart murmur
per se is not a contraindication, but rather a caution
for general anaesthesia in a patient not showing clinical signs. The drug selection to achieve general anaesthesia and analgesia may require a patient tailored
approach, especially if the murmur is due to cardiac
pathology.
• Murmurs are audible evidence that there is turbulent blood flow through the heart. The murmur
is graded according to how loud the murmur is
compared to the lub-dub sounds heard during
the cardiac cycle.4 The lower the grade of the
murmur (III and less) the less reliable it is to indicate the severity of the pathology.4, 9 Therefore,
on detecting a heart murmur, further investigation is required to determine the severity of the
pathology and if the murmur is cardiac in origin
or not.
Post-murmur-detection clinical investigation
Two critical clinical investigation aims need to be
achieved. First, is to determine if the pathology is due
to cardiac or non-cardiac processes. Second, is to determine if the patient is otherwise clinically affected by
the presence of the murmur.1, 2
•
Cardiac related pathologies include valve stenosis or insufficiency (disease or traumatic), atrial
or ventricular septal defects, or complex cardiac
malformations (e.g. tetralogy of Fallot). Non-cardiac pathologies include vascular anomalies (e.g.
Figure 1: Evaluation of blood pressure by doppler
•
•
patent ductus arteriosus), altered viscosity (e.g.
anaemia), altered flow velocity (e.g. hyperdynamic flow), or obstruction to flow through the heart
(e.g. thrombus, air emboli).4
Exercise tolerance is considered an excellent
marker to gauge cardiovascular fitness and risk
for general anaesthesia, whereby, the more tolerant the patient is to exercise the lower the risk of
general anaesthesia. Perceptive questioning could
clarify the patient’s exercise tolerance.
The clinician should be suspicious if the patient
presents with a murmur and tachycardia, delayed
capillary refill time, pale mucous membranes and
a history of being “sleepy” or mostly inactive during the day. These findings could suggest that the
patient is not cardiovascular stable and thus of a
higher anaesthetic risk. The resultant pathophysiology is invariably related to a decrease in cardiac
output which translates into a decrease in perfusion of oxygen to metabolically active tissues.
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