Right ventricular hypertrophy

Right ventricular hypertrophy (RVH) is a condition defined by an abnormal enlargement of the cardiac muscle surrounding the right ventricle. The right ventricle is one of the four chambers of the heart. It is located towards the lower end of the heart and it receives blood from the right atrium and pumps blood into the lungs. Since RVH is an enlargement of muscle it arises when the muscle is required to work harder. Therefore, the main causes of RVH are pathologies of systems related to the right ventricle such as the pulmonary artery, the tricuspid valve or the airways. RVH can be benign and have little impact on day to day life or it can lead to conditions such as heart failure, which has a poor prognosis.

On physical examination, the most prominent features are due to the development of right sided heart failure. These can include a raised jugular venous pressure, ascites, left parasternal heave and a tender, enlarged liver on palpation. On inspection, patients may be chronically ill, cyanotic, cachectic and occasionally jaundiced. On auscultation, an accentuated second pulmonary sound (S2), a third heart sound termed a ‘right ventricular gallop’, as well as a systolic murmur over the tricuspid area accentuated by inspiration may be present. On occasion, the systolic murmur can be transmitted and auscultated over the liver. Less typically, diastolic murmur may also be heard as a result of pulmonary insufficiency. RVH occurs in approximately 30% of these cases. PH is broadly split into five categories by the World Health Organization, based on the underlying cause. The incidence of RVH varies between the groups. Common causes of PH include chronic obstructive pulmonary disease (COPD), pulmonary embolism, and other restrictive lung diseases. RVH often occurs as a result of these disorders. RVH is seen in 76% of patients with advanced COPD and 50% of patients with restrictive lung disease.

Right ventricular hypertrophy can be both a physiological and pathophysiological process. It becomes pathophysiological (damaging) when there is excessive hypertrophy. The pathophysiological process mainly occurs through aberrant signalling of the neuroendocrine hormones; angiotensin II, endothelin 1 and the catecholamines (e. g. noradrenaline).

Angiotensin II and endothelin 1 are hormones that bind to the angiotensin (AT) and endothelin (ET) receptors. These are G protein coupled receptors that act via internal signalling pathways. Through several intermediates, these pathways directly or indirectly increase reactive oxygen species (ROS) production causing accumulation in myocardial cells. This can subsequently induce necrotic cell death, fibrosis, and mitochondrial dysfunction. This has been demonstrated in animal studies. Protein Kinase C (PKC) is an intermediate molecule in the signalling pathway and mice lacking PKC shown resistance to heart failure compared to mice overexpressing PKC which shown heart dysfunction. Targeting the renin–angiotensin (RAAS) system (using angiotensin converting enzyme inhibitors and angiotensin receptor blockers) are a well recognized clinical approach for reversing maladaptive cardiac hypertrophy independently of blood pressure.

Echocardiography can be used to directly visualise right ventricular wall thickness. The preferred technique is the trans oesophageal approach giving a view of 4 chambers. The normal thickness of a right ventricular free wall ranges from 2 5 millimetres, with a value above 5 mm considered to be hypertrophic.

It is important to understand that right ventricular hypertrophy in itself is not the main issue, but what right ventricular hypertrophy represents is. Right ventricular hypertrophy is the intermediate stage between increased right ventricular pressure (in the early stages) and right ventricle failure (in the later stages). As such, management of right ventricular hypertrophy is about either preventing the development of right ventricular hypertrophy in the first place, or preventing the progression towards right ventricle failure. Right ventricular hypertrophy in itself has no (pharmacological) treatment. Surgery is considered in more serious situations where the patient is severely symptomatic. Surgical options include either: replacement of the valve or repair of the valve (termed annuloplasty). When it comes to replacement, there is a choice between a bioprosthetic valve or a mechanical valve, depending upon the specific patient characteristics. Mechanical valve has greater durability, but requires anti coagulation to reduce the risk of thrombosis. Treatment of pulmonary hypertension will depend on the specific cause of the pulmonary hypertension. On top of this, the following may also be considered: diuretic, oxygen and anti coagulant therapy.