Left ventricular hypertrophy (LVH) is a thickening of the muscular wall of the heart’s most powerful pumping chamber, the left ventricle. This chamber pushes oxygenated blood out through the aorta to the rest of the body. An electrocardiogram (ECG or EKG) is a non-invasive test that records the heart’s electrical activity. This procedure is often a first step in assessing heart health, as it can reveal clues about the heart’s size and function, including signs of LVH.
Identifying LVH on an ECG
An electrocardiogram provides a window into the heart’s electrical system, as a thicker heart muscle generates stronger electrical signals. This increased electrical output is the principle for identifying potential LVH on an ECG. Clinicians see this as larger waveforms in the QRS complex, which represents the electrical activation of the ventricles. A thickened ventricle is like a bigger speaker producing a “louder” sound, which translates to higher voltage on the ECG.
To standardize the interpretation of these signals, methods known as voltage criteria are used. Among the most established are the Sokolow-Lyon criteria, which involve a calculation. A clinician measures the S-wave depth in lead V1 and adds it to the R-wave height in lead V5 or V6. If this sum exceeds 35 millimeters, it suggests LVH.
Another widely recognized method is the Cornell voltage criteria. This calculation adds the S-wave depth in a different chest lead (V3) to the R-wave height in a limb lead (aVL). Because body composition can influence ECG signals, the thresholds for the Cornell criteria are adjusted for gender.
Beyond the size of the electrical waves, an ECG can offer more detail through non-voltage criteria. A significant one is the “left ventricular strain” pattern. This pattern appears as specific changes in the ST segment and T-wave portions of the ECG, which follow the QRS complex. A downsloping ST segment and an inverted T-wave in certain leads can indicate the thickened muscle isn’t receiving adequate oxygen. The presence of a strain pattern with high voltage criteria is a more telling indicator of advanced hypertrophy.
Underlying Causes of Left Ventricular Hypertrophy
Left ventricular hypertrophy is the heart’s adaptive response to a sustained period of increased workload. When the left ventricle is forced to pump harder to circulate blood, its muscular wall gradually thickens to meet the heightened demand. This process is similar to how skeletal muscles, like the biceps, grow larger from weightlifting. The heart muscle adapts to its burden, but this change is not always beneficial long term.
The most common cause is chronic high blood pressure (hypertension). When blood pressure is consistently elevated, the left ventricle must generate more force with every beat to push blood into the arteries against this higher resistance. Over time, this effort triggers the muscular walls of the ventricle to thicken. Effectively managing blood pressure is a primary strategy for preventing or helping to reverse this process.
Another common cause is a condition called aortic valve stenosis. The aortic valve acts as a gateway between the left ventricle and the aorta. Stenosis means this valve has become narrowed and stiff, making it difficult to open properly. This narrowing creates a bottleneck, forcing the left ventricle to work much harder to squeeze blood through the smaller opening.
While hypertension and aortic stenosis are the primary causes, other factors can also lead to LVH. Certain genetic conditions, such as hypertrophic cardiomyopathy, cause the heart muscle to thicken without an external pressure trigger. Intense and prolonged athletic training can lead to a physiological form of LVH, often called “athlete’s heart,” which is considered a benign adaptation to physical conditioning.
Diagnostic Accuracy and Further Testing
While the ECG is a valuable screening tool for left ventricular hypertrophy, it is not a definitive diagnostic test. Its primary limitation is diagnostic accuracy. An ECG can fail to detect LVH even when it is present, a characteristic known as low sensitivity, with studies showing that various criteria may identify only a small fraction of confirmed cases.
Conversely, an ECG can suggest LVH in individuals who do not have the condition, leading to a false positive result. This is common in populations such as young, thin individuals or highly trained athletes. Their natural heart structure might produce strong electrical signals that mimic the voltage criteria for LVH.
When an ECG suggests the presence of LVH, the standard next step is to perform an echocardiogram. Often referred to as an “echo,” this procedure uses ultrasound waves to create detailed, real-time images of the heart. Unlike an ECG, which measures electrical activity, an echocardiogram directly visualizes the heart’s structures. This allows a clinician to see the heart walls, measure their exact thickness, and assess how well the chambers and valves are functioning.
The echocardiogram is considered the “gold standard” for diagnosing LVH because it provides a direct anatomical measurement of the left ventricular mass and wall thickness. It can definitively confirm or rule out the presence of hypertrophy suggested by an ECG. This detail is necessary for an accurate diagnosis and for determining the severity of the condition to guide treatment.