Advances in science and technology have led to greater insight into complex cardiomyopathies
Ms Mary Mooney, Lecturer, School of Nursing and Midwifery, Trinity College Dublin and Ms Jingli Li, Specialist Coronary Care Staff Nurse, Tallaght Hospital, Dublin
Cardiomyopathy is contemporarily defined as a disease of the heart muscle with structural and functional abnormality in the absence of known cardiovascular causes, including hypertension, ischemic heart disease, valvular disease, or congenital heart disease. 1
However, clinically, the term “cardiomyopathy” has also been applied to diseases of known cardiovascular causes, such as “ischaemic cardiomyopathy” or “hypertensive cardiomyopathy”.2
Broadly speaking, cardiomyopathies can be classified according to morphological and functional criteria and grouped into familial and non-familial subtypes irrespective of the presence of extra-cardiac disease (Figure 1).
(click to enlarge)
However, cardiomyopathy classification has historically been divisive across cardiac associations. The most recently proposed and generally accepted classification system proposes a descriptive phenotype and genotype incorporating five characteristics, using the mnemonic MOGES, as shown in Table 1.3
(click to enlarge)
Irrespective of classification, cardiomyopathies are accepted to be a heterogenous group of myocardial diseases associated with mechanical and/or electrical dysfunction. Cardiomyopathy is the leading diagnosis among cardiac transplantation recipients internationally and is one of the leading causes of sudden cardiac death. The most commonly seen cardiomyopathies include dilated, hypertrophic, arrhythmogenic and restrictive cardiomyopathies. For this paper, a brief explanation of each of these is provided in the next section. Other cardiomyopathies include Takotsubo, and right and left ventricular cardiomyopathy.
Dilated cardiomyopathy
Dilated cardiomyopathy is a non-ischaemic cardiomyopathy that is characterised by ventricular dilatation, causing cardiac enlargement and impaired ventricular contraction, without thickening of the ventricular walls.4
Most are idiopathic, but the condition has been linked with excessive alcohol intake, untreated hypertension, viruses and familial or genetic factors.5
Hypertrophic cardiomyopathy
Hypertrophic cardiomyopathy is a complex autosomal dominant inherited condition affecting approximately one in every 500 individuals of any age group. It generally affects the left ventricle, but can also affect the intraventricular septum and right ventricle. It is characterised by enlargement of the cardiac muscle cells, which in turn cause the ventricular walls to thicken, but not dilate. 6 Therefore, the ventricle may be of normal size, but the muscle thickening may inhibit ejection of blood from the ventricle; the term hypertrophic obstructive cardiomyopathy is often used to describe this phenomenon. Changes at cellular level can disrupt the cardiac electromechanical sequences, thereby predisposing the individual to rhythm disruption and sudden cardiac death.
Arrhythmogenic cardiomyopathy
This condition, formally referred to as arrhythmogenic right ventricular cardiomyopathy, is an important cause of cardiac death in those under 35 years and is more prevalent in males.6 It involves the gradual replacement of right ventricular myocytes with fibrous and adipose tissue. In severe cases, the left ventricle can also be involved. It is suggested that it is transmitted by an autosomal dominant mode of inheritance. It may manifest in prolonged ventricular activation with ventricular tachyarrhythmias, left bundle branch block and sudden cardiac death. 4
Restrictive cardiomyopathy
Restrictive cardiomyopathy is rare. It is characterised by a reduction in ventricular diastolic function. Owing to impaired diastole, there is reduced myocardial compliance, resulting in raised ventricular pressure and eventual diastolic heart failure. Because of these pathophysiological events, atrial enlargement occurs while systolic function remains unchanged. Restrictive cardiomyopathy can be idiopathic, infiltrative due to amyloid or, for example, due to drug-related endomyocardial pathology.
Case study 1
Hypertrophic cardiomyopathy
Background: A 64-year old man was admitted to the coronary care unit. On admission, he was very dyspnoeic and had notable sacral and pedal oedema, which were explained by an 11 KG weight gain over the previous six weeks. His vital signs were within normal parameters. On auscultation, third and fourth heart sounds were heard, in addition to a systolic murmur, which was clearly heard at the left sternal border when the patient was asked to perform the Valsalva manoeuvre. The fourth heart sound was caused by forceful atrial contraction against the hypertrophied and non-compliant ventricle.
Previous genetic testing showed the presence of an autosomal dominant inheritance. He had been diagnosed with restrictive variant hypertrophic cardiomyopathy 10 years previously. His coronary angiogram at that time showed no obstructive disease. He had a history of hypertension, atrial fibrillation, embolic CVA in 2015 and had a permanent pacemaker insertion in 1997. He was a smoker and did not adhere well to prescribed medications.
ECG: Soon after admission, a non-sustained run of ventricular tachycardia (VT) was noted during cardiac monitoring. His ECG showed atrial fibrillation with left bundle branch block and indications of left ventricular hypertrophy. The p wave was enlarged, indicating atrial enlargement. BNP was 1,733 (normal value < 100pg/mL).
Echo: Bilateral ventricular enlargement with wall thickness 2.5-2.8cm, systolic impairment and diastolic dysfunction. Ejection fraction 40%, with mild tricuspid and mitral regurgitation. Moderate-severe dilation of the right ventricle and left atrium noted.
Outcome: After five days of nursing and medical treatment, the patient had reverted to his baseline dry weight. Physical signs and symptoms improved. Intensive education was provided, and an appointment made for follow-up at a Cardiac Risk in the Young (CRY) clinic.
Case study 2
Dilated cardiomyopathy
Background: A 46-year-old gentleman was admitted to the coronary care unit with progressive shortness of breath for the previous 12 weeks. There was associated ankle and leg swelling, in addition to paroxysmal nocturnal dyspnoea and orthopnoea. There were no anginal symptoms or palpitations and no noted risks for coronary artery disease. On examination a raised jugular venous pressure was noted, in addition to bi-basal crepitations but no murmur was heard. Additional history included an average alcohol intake of 70 units per week and he was a current smoker.
ECG: The ECG showed a sinus rhythm with frequent ectopic beats, in addition to a noted left posterior fascicular hemiblock. He had an asymptomatic run (67 beats) of ventricular tachycardia, which was subsequently treated with IV magnesium 5g stat and he was commenced on bisoprolol 2.5mg daily.
Echo: The echo for this patient showed a dilated left ventricle with severe left ventricular dysfunction. There was mild-moderate mitral valve regurgitation. The ejection fraction was 30%, and the BNP was 2050. Troponion levels were normal. A chest x-ray showed cardiomegaly and congestion.
Medications: Two doses of metolazone 2.5mg stat, were administered, in addition to intravenous furosemide 80mg BD, bisoprolol 5mg daily, sacubitril/valsartan 24mg/26mg BD and eplenerone 25mg daily.
Outcome: While cardiac magnetic resonance imaging (CMRI) is considered the gold standard for assessment accuracy, it was not used in the initial stages of management of this patient. The echo was readily available and provided enough information on which to base the initial treatment. The patient had an angiogram which showed mild and non-obstructive coronary artery disease. An arrangement was made for the patient to have a cardiac MRI, as part of the on-going follow-up treatment. Additionally, a referral was made for the patient to be followed up with the heart efficiency team.
Case study 3
Arrhythmogenic cardiomyopathy
Background: A 24-year-old athletic male was admitted to the coronary care unit following a witnessed cardiac arrest, with successful defibrillation. He had no medical history of note, but he reported episodes of palpitations in recent weeks and was lightheaded on a few occasions. He was stable on admission to the unit.
ECG: A piece of original rhythm strip showed ventricular fibrillation (VF) and it was reported that he was in VF for at least 30 seconds. On admission, the ECG showed a sinus rhythm with right bundle branch block and T wave inversion in leads V2 and V3. An epsilon wave was also present on the QRS complex, which is a typical finding in arrhythmogenic right ventricular dysplasia, secondary to the delay in repolarisation.
Echo: The echo for this patient provided limited information and only showed a hypokinetic, dilated right ventricle, with right ventricular wall-thinning and an ejection fraction of 45%. While left ventricular involvement has been reported in some patients, 7 this was not the case for this individual.
Medications: The patient was treated with enalapril 2.5mg BD and bisoprolol 5mg daily.
Outcome: Management included familial genetic screening, referral to a CRY clinic and preparation for the implantation of a cardioverter defibrillator. Beyond hospital admission, he was advised against participation in competitive sports and vigorous athletics. However, evidence to support participation in sport with an ICD is growing.8 The patient was on maximum medication therapy on discharge and follow-up included cardiac MRI, Holter monitoring and exercise stress testing.
Conclusion
Cardiomyopathies are complex conditions, comprising various typologies and classifications. Thanks to advances in science and technology, our knowledge and understanding of these disorders has increased significantly. Those who suffer from these conditions are predisposed to sudden cardiac death and disability, owing to the mechanical and electrical dysfunctions.
Treatment strategies reflect those of heart failure management and comprise, in part, pharmacological interventions, device implantation and education and support strategies. Because of the familial links with these conditions, screening and genetic testing is elementary to the initial and ongoing management of patients.
The establishment of Cardiac Risk in the Young (CRY) clinics has been successful to the follow-up and support of patients, who should be referred there, where appropriate. Current clinical trials involving stem cell and gene therapy may open doors to improved outcomes for future patients diagnosed with cardiomyopathy.
Mary Mooney is an assistant professor in Nursing at Trinity College Dublin and Jingli Li is a specialist coronary care staff nurse at Tallaght Hospital
References
Elliott P, Andersson B, Arbustini E, Bilinska Z, Cecchi F, Charron P, Dubourg O, Kuhl U, Maisch B, McKenna WJ, Monserrat L, Pankuweit S, Rapezzi C, Seferovic P, Tavazzi L, Keren A. Classification of the cardiomyopathies: a position statement from the European Society Of Cardiology Working Group on Myocardial and Pericardial Diseases. European Heart Journal 2018; 29(2): 270-276
Cooper L. Definition and Classification of the Cardiomyopathies 2017. Retrieved from https://www.uptodate.com/contents/definition-and-classification-of-the-cardiomyopathies?search=cardiomyopathy&source=search_result&selectedTitle=1~150&usage_type=default&display_rank=1 on 3 April, 2019
Arbustini E, Narula N, Dec GW, Reddy KS,Greenberg B, Kushwaha S, Marwick T, Pinney S, Bellazzi R, Favalli V, Kramer C, Roberts R, Zoghbi W, Bonow R, Tavazzi L, Fuster V & Narula J The MOGE(S) Classification for a Phenotype – Genotype Nomenclature of Cardiomyopathy; Endorsed by the World Heart Federation. Journal of American College of Cardiology 2013;62(22):2046-2072
Braunwald E & Marian A. Cardiomyopathies: An overview. Circulation Research 2017; 211: 711-721
Browne L & Mooney M. Understanding cardiomyopathy. Continuing Education Series in Cardiology; World of Irish Nursing. MedMedia Group, Dublin. 2005;13(8):41
Gunaratnam K, Wong L, Nasis A, Ellims A, Nandurkar D, Soo G, Cameron J & Troupisa J. Review of cardiomyopathy imaging. European Journal of Radiology 2013; 82:1763-1775
Corrado D, Wichter T, Link M, Hauer R, Marchlinski F, Anastasakis A, Bauce B, Basso C, Brunckhorst C, Tsatsopoulou A, Tandri H, Paul M, Schmied C, Pelliccia A, Duru F, Protonotarios N, Estes M III, McKenna W, Thiene G, Marcus F & Calkins H. Treatment of Arrhythmogenic Right Ventricular Cardiomyopathy/Dysplasia. An International Task Force Consensus Statement. Circulation 2015;132: 441-453
Zorzi A, Pelliccia A & Corrado d. Inherited cardiomyopathies and sports participation. Netherlands Heart Journal 2018;26(3):154-165
(click to enlarge)
