Cardiomyopathy: A Brief Introduction
Cardiomyopathy is a diverse group of serious disorders in which heart musculature develops structural or functional abnormalities, thus making it difficult for the cardiac muscles to pump blood into the systemic vessels. This pathology may lead the ventricles of heart to become dilated, rigid or even hypertrophied. The disease maybe genetic or acquired. However, the end-result remains the same which involves a gradually declining cardiac output.
Different Types of Cardiomyopathy
In general, there are three different variations of cardiomyopathy, as described below:
1. Dilated Cardiomyopathy (DCM)
This is the most common type of cardiomyopathy. The dilated variant of cardiomyopathy or DCM features a uniform enlargement of the left and/or right ventricle of the heart. The disease can be linked to a series of causative factors such as excessive alcohol consumption, various disorders of metabolism, inflammation of the cardiac musculature or myocarditis, and autoimmune conditions. In addition, genetic factors also play a vital role in its pathophysiology.
Clinical Manifestations
DCM can be asymptomatic or present itself in the form of following clinical features:
- Shortness of breath on lying flat
- Poor exercise tolerance
- Edema or swelling in the feet
- Rapid and irregular heartbeat or arrhythmia
- Worsening of heart condition may lead to acute heart failure, or may even result in sudden cardiac death.
2. Hypertrophic Cardiomyopathy (HCM)
Rather than dilatation of the cardiac chambers, this type of cardiomyopathy leads to gradual thickening (~15 mm) or hypertrophy of the cardiac muscles located in the ventricles as well as the septum in between them. An important event here is that uniform thickening of the muscle wall may cause a significant reduction in the left ventricular outflow, thereby leading to poor cardiac output and eventually heart failure. In this phase, the disease is often termed as hypertrophic obstructive cardiomyopathy (HOCM). Its etiology has been mostly traced to hereditary causes.
Clinical Manifestations
Following are a few major clinical manifestations in HCM:
- Chest pain
- Palpitations or arrhythmia’s
- Shortness of breath upon lying down
- Poor exercise tolerance
- The disease could be asymptomatic initially and present itself in the form of sudden cardiac arrest among younger or elderly individuals.
3. Restrictive Cardiomyopathy (RCM)
This is perhaps the least common variety of cardiomyopathy. In this disease, the walls of the heart chambers gradually become stiff which makes them non-compliant. This results in insufficient expansion as well as decreased contractility of the ventricular musculature. The underlying etiology maybe genetic or acquired. This disease is increasingly prevalent among individuals diagnosed with amyloidosis, sarcoidosis, hereditary hemochromatosis, and glycogen or glycolipid storage disorders.
Clinical manifestations
- Poor exercise tolerance
- Shortness of breath (especially on lying down)
- Foot swelling
- Cardiac arrhythmia’s
- Low blood pressure or hypotension
- Sudden cardiac death can occasionally take place
4. Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC)
This disease is characterized by a gradual atrophy of cardiac musculature in the right ventricle which is then substituted by non-contractile fatty tissue. A number of bulky, fat-filled deposits are formed in the walls of right ventricle which may lead to bulging of the myocardium. This eventually leads to right ventricular heart failure. This disease has been identified as a familial condition in at least half of the affected individuals.
Surgical Anesthesia for Patients with Cardiomyopathy
General anesthesia is an essential pre-requisite prior to any major surgery. By definition, a major surgery is any operative procedure which can last beyond 1-2 hours and therefore, requires special anesthesia considerations. Before sedating any patient for a major operation, the surgical team must ensure that the patient meets all the standard criteria for anesthesia administration. In other words, the patient’s cardiovascular function must be optimized so as to minimize the risk of sudden cardiac arrest. This is an even tougher challenge for the patients who have been diagnosed with cardiomyopathy.
Aims of a Safe Anesthesia Technique
Medical experts recommended that the anesthesia team must adhere to the following aims during surgical intervention in the patients having a co-existing cardiomyopathy:
- Prevention of any disruption in heart rate and rhythm
- Maintenance of the patient’s cardiac volumes and blood pressure
Anesthesia Considerations
The following are a few important measures to be adopted during anesthesia administration in such patients:
- Anesthesia drugs:
The most ideal candidate must be selected for anesthesia induction and maintenance. As the inhalational agents are known to alter cardiac contractility, intravenous (IV) drugs maybe preferably used. These include IV propofol and etomidate. Opioid analgesics (e.g., fentanyl ) can also be useful. Overdosing on any agent should be best avoided.
- Peri-operative Monitoring of heart:
Direct arterial catheterization maybe carried out for monitoring blood pressure. In addition, transoesophageal echocardiography can also be a reliable tool for evaluation of cardiac physiology in the perioperative period.
- Optimization of heart contractility:
Heart rate should be continuously monitored and if necessary, stimulating agents (e.g., dobutamine or dopamine) can be administered to boost the cardiac output.
- Postoperative evaluation:
Finally, a meticulous postoperative cardiac care will help a patient undergo speedy recovery from the stress of surgery.
Conclusion
Before conducting any major surgery, an individual must be thoroughly screened for cardiomyopathy and if detected, an appropriate anesthesia plan must be followed in order to achieve a favorable outcome.
References
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- Jefferies JL, Towbin JA. Dilated cardiomyopathy. Lancet. 2010;375(9716):752-762.
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- Muchtar E, Blauwet LA, Gertz MA. Restrictive Cardiomyopathy: Genetics, Pathogenesis, Clinical Manifestations, Diagnosis, and Therapy. Circ Res. 2017;121(7):819-837.
- Orgeron GM, Crosson JE. Arrhythmogenic right ventricular dysplasia/cardiomyopathy. Cardiol Young. 2017 Jan;27(S1):S57-S61.
- Ibrahim IR, Sharma V. Cardiomyopathy and anaesthesia. BJA Education. 2017;17(11):363-369.