Catecholamines can act on the alpha-adrenergic receptors and beta-adrenergic receptors which are G-protein coupled receptors. This binding initiates the same intracellular signalling pathways as angiotensin and endothelin. There is also activation of cAMP and an increase in intracellular Ca2+ which leads to contractile dysfunction and fibrosis. Others
Hormones are not the only cause of RVH. Hypertrophy can also be caused by mechanical forces, mTOR pathways, nitric oxide and immune cells. Immune cells can cause hypertrophy by inducing inflammation. Diagnosis
The two main diagnostic tests used to confirm right ventricular hypertrophy are electrocardiography and echocardiography. Electrocardiography
The use of electrocardiogram (ECG) to measure cardiac chamber hypertrophy is well established but since the left ventricular activity is dominant on the ECG a large degree of RVH is often required for any detectable changes. Nonetheless, the ECG is used to assist with the diagnosis of RVH. A post mortem study on 51 adult male patients concluded that anatomical RVH may be diagnosed using one or more of the following ECG criteria:
Right axis deviation of more than (or equal to) 110° (see hexaxial reference figure)
R-wave dominant over S-wave in V1 or V2
S-wave dominant over R-wave in V6However, the American Heart Association recommended the use of additional diagnostic tests to diagnose RVH because no single criteria or set of criteria were considered sufficiently reliable. Echocardiography
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. Treatment
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. Treating the cause
Since the main causes of right ventricular hypertrophy is tricuspid regurgitation or pulmonary hypertension (discussed above), management involves treatment of these conditions. Tricuspid regurgitation is typically treated conservatively by aiming to treat the underlying cause and following up the patient regularly. 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.