ECG cardiac hypertrophy and enlargement

Definitions & Key takeaways

Myocardial hypertrophy refers to the increase in the thickness of the heart's muscular wall, and myocardial enlargement refers to hypertrophy associated with the dilation of the cardiac chambers, typically the atria. Both myocardial hypertrophy and enlargement present specific findings on ECG and can help to identify which chamber of the heart that's involved. For example, the right atrial enlargement shows a big P wave in lead II and V1, whereas the right ventricular hypertrophy shows a big R wave in V1 and a big S wave in V5 and V6.

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Introduction0:00–0:55

An electrocardiogram - an ECG - or the dutch and german version of the word - elektrokardiogram or EKG, is a tool used to visualize “gram” the electricity “electro” that flows through the heart “cardio”.
An ECG tracing specifically shows how the depolarization wave moves during each heartbeat - which is a wave of positive charge - looks from the perspective of different sets of electrodes.
This particular set of electrodes is called lead II, with one electrode on the right arm and the other on the left leg, so essentially when the wave’s moving toward the left leg electrode, you get a positive deflection, like this big positive deflection correspond to the wave moving down the septum.
There are lots of things to look for when reading an ECG, one of them includes figuring out if part of the heart has undergone hypertrophy or enlargement.Hypertrophy means that a heart’s muscular wall has increased in thickness while dilation refers to an increase in the volume of the chamber.

Hypertrophy0:55–1:27

The term enlargement is generally used when both hypertrophy and dilation occur together, and this is what typically happens in the atria.
In contrast, the ventricles often undergo hypertrophy without dilation. An ECG can show evidence of hypertrophy and enlargement in all of the heart’s four chambers - so let’s go through them one by one.
Normally, atrial depolarization produces a pretty normal looking - symmetric P wave. In right atrial enlargement, all of that extra right atrial muscle tissue results in a large P wave in leads V1 and V2, often over 1.5 mm, as well as in the inferior leads - leads II, III, and aVF, often over 2.5 mm.

Right Atrial Enlargement1:27–2:05

One reason why right atrial enlargement develops is that there can be a stenotic or narrowed tricuspid valve that makes it more difficult for the atria to eject blood into the ventricles, and in response, the right atrium enlarges.
In left atrial enlargement, the left atrium has extra muscle tissue and that results in a P wave with two peaks in lead II, with the entire thing stretching out over 110 ms, and a gap of over 40 ms separating the two peaks.

Left Atrial Enlargement2:05–2:55

In lead V1 the P wave is biphasic, meaning that it looks like a hill with a valley alongside it. The negative portion is usually 1 mm deep and lasts for more than 40 ms.Left atrial enlargement also develops from a stenotic valve, but this time it’s the mitral valve that causes the left atrium to get bigger.Normally, the QRS complex is mostly negative in lead V1 because the large left ventricle, which carries the greatest amount of muscle tissue, is oriented down and away from this electrode.
In right ventricular hypertrophy, the thicker right ventricle helps to counterbalance the left ventricle and makes lead V1 more positive.
More specifically, it makes the R wave bigger, which is the upward deflection of the QRS complex. In fact, a dominant R wave in V1 is a classic sign of right ventricular hypertrophy and it’s defined as one that is over 7mm tall or 7 little boxes and is larger than the S wave, making the R/S ratio > 1.

Right Ventricular Hypertrophy2:55–4:38

In V5 and V6, another classic sign of right ventricular hypertrophy is a dominant S wave in V5 or V6 - meaning that it’s over 7mm deep, again 7 little boxes, and bigger than the R wave, making the R/S ratio < 1.>
Typically, there’s also right axis deviation in right ventricular hypertrophy resulting in an axis of 110 degrees or more.
In right ventricular hypertrophy the QRS complex is <120ms, meaning that it’s not longer than normal. This is important because it means that the changes can’t be the result of something like a right bundle branch block which would cause a prolonged QRS complex.>
Right ventricular hypertrophy can develop for a number of reasons - a common one being pulmonary hypertension, which makes sense because the right ventricle has to build up muscle to push blood into the lungs.
In left ventricular hypertrophy the pattern is almost the opposite of what happens in right ventricular hypertrophy. Lead V1 has even more positive charge traveling away from it than usual, making the S wave really deep.
Meanwhile, lead V5 and V6 are located on the side of the left ventricle, and therefore have an enormous R wave. The most commonly used voltage criteria to identify left ventricular hypertrophy is that adding up the S wave in V1 and the tallest R wave in V5 or V6 has to be over 35 millimeters, or 35 little boxes.

Left Ventricular Hypertrophy4:38–5:46

Additional criteria include things like having an R wave that goes on for longer than usual - typically over 50ms, ST segment depression, and T wave inversion in V5 or V6.
These are signs that the left ventricle is straining during muscle contraction. Left ventricular hypertrophy commonly develops due to systemic hypertension, or elevated systemic blood pressure, since the left ventricle needs more muscle so that it can eject blood against higher pressures.
All right, as a quick recap… Right atrial enlargement shows a big P wave in lead II and V1, whereas left atrial enlargement has a biphasic P wave in lead V1 and a double-humped P wave in lead II.
Right ventricular hypertrophy shows a big R wave in V1 and a big S wave in V5 and V6, whereas left ventricular hypertrophy shows the opposite - an enormous S wave in V1 and a large R wave in V5 and V6 adding up to over 35 mm.

Review5:46–6:19

big P wave in lead to Envy. One wears left.
Atrial enlargement has a biphasic P wave in lead V1 with a negative component greater than 1 millimeter deep and lasting more than 40 millisecond.
If you wave in lead 2, Right. Ventricular hypertrophy shows a big are way Vincy.
One in a big ass waving, B5 and B6 West left. Ventricular.
Hypertrophy shows the opposite. A huge S Wave in V1 and a huge 75 and B6 adding up to over