Left ventricular hypertrophy
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Left ventricular hypertrophy (LVH) is present when the left ventricular mass is increased. It is a common condition, typically due to systemic hypertension, and it increases with age, obesity and severity of hypertension.
Studies have demonstrated a prevalence on echocardiography of 36-41% in hypertensive patients 1.
When mild, left ventricular hypertrophy is usually asymptomatic. As it worsens, symptoms of congestive heart failure gradually arise.
Left ventricular hypertrophy may result from either increased pressure or volume afterload on the heart. Much more rarely it may result from genetic conditions. The relationship between obesity and left ventricular hypertrophy is complex.
A large number of conditions can cause left ventricular hypertrophy.
- hypertension: pressure overload
- valvular heart disease
- genetic diseases
- severe physical exercise
Robust reference data exists for quantifying left ventricular size with echocardiography, using guidelines from the American Society of Echocardiography and the European Association of Cardiovascular Imaging. Similar validated data does not (yet) exist for cardiac MRI/CT and therefore most use the echo data for measurements on MRI and CT.
Transthoracic echocardiography is an important screening tool to detect left ventricular hypertrophy; favorable features include near universal availability, absence of ionizing radiation and superb temporal resolution. Like any ultrasound-based technique, echocardiography is more dependent on the operator than CT/MRI and is more affected by patient factors.
The linear method, utilizing either two dimensional or M-mode derived measurements, is often utilized in screening echocardiograms. A parasternal long (or short) axis view is obtained, a cine-loop recorded, and a frame is chosen at end-diastole, immediately prior to mitral valve closure. The following measurements are then obtained 2;
- thickness of the interventricular septum (IVSd)
- thickness of the posterior/inferolateral wall (PWTd)
- internal diameter of the left ventricle (LVIDd)
- serves as the denominator in the relative wall thickness (RWT) calculation, with the numerator being (PWTd x 2)
The left ventricular mass index is then derived; values exceeding 95 or 115 g/m2 in females and males respectively traditionally define left ventricular hypertrophy. Further stratification of both the normal and hypertrophic left ventricle then proceeds using relative wall thickness, which subdivide the former into normal ventricles and those with concentric remodeling, and the latter into eccentric and concentric hypertrophy 3.
Cardiac MRI (CMR) is the current gold standard for evaluation of left ventricular hypertrophy, with the ability to measure multiple other myocardial parameters simultaneously. Its spatial resolution is poorer than echo/cardiac CT, takes longer to perform than either echo or CT, and has relative limitations in those with implanted cardiac devices (e.g. mechanical valves, pacemakers, etc.).
Cardiac CT is currently the least favored technique for assessment of left ventricular hypertrophy due to the relatively high radiation dose. It is a fast technique, with high spatial resolution, although its temporal resolution is poor.