Ventricular hypertrophy is reflected in QRS axis deviation towards the hypertrophied ventricle, increased amplitudeThe height or depth of waves and complexes of an ECG in millimetres; represents millivolts where 10 mm is 1 millivolt with a properly calibrated monitor. 1. Six Second ECG Guidebook (2012), T Barill, p. 190 in the QRS complexThe electrical representation of ventricular depolarization; the atrial repolarization is also a part of the QRS. ECG interpretation relies heavily on the QRS complex. The QRS complex represents the depolarization of the ventricles. The repolarization of the atria is also..., altered R wave progressionThe phenomenon of R wave progression utilizes the following six leads: V1, V2, V3, V4, V5, V6. The chest leads provide information on the sagittal plane from the anterior surface across to the lateral surface of the heart. Notice in..., and possibly signs of ventricular strainWith severe ventricular hypertrophy, the myocardium can thicken to such a degree that the blood supply to the subendocardium (inner lining of the heart just inside the endocardium) can diminish. As a result, the endocardium is particularly susceptible to hypoxia.... – ST depressionThe downward placement of the ST segment greater than 1 mm from the isoelectric line; suggestive of cardiac ischemia, but also may point to ventricular hypertrophy, digoxin use, and pericarditis among other possibilities. Between the QRS complex and the T... and T wave inversionAn inverted T wave can point to cardiac ischemia among other causes. Ischemia to the epicardium prolongs ventricular repolarization to this area. This extended repolarization of the epicardium removes the delay between the repolarization of the endocardium and the repolarization....
Note that ST changes can occur from conditions other than myocardial ischemiaInsufficient supply of oxygen to meet the oxygen demands of tissue. Anaerobic metabolism becomes increasingly important during periods of ischemia. Ischemia results from an inadequate blood flow that fails to meet the oxygen demands (energy demands) of tissues. If tissues.... A depressed and upward sloping ST segmentSegment (line) between the end of the QRS complex and the beginning of the T wave; the end of the QRS is marked by the J point. Between the QRS complex and the T wave, lies the ST segment. The... can represent ventricular hypertrophy.
A reversed R waveFollowing the depolarization of the interventricular septum, ventricular depolarization then progresses from the endocardium through to the epicardium across both ventricles producing an R wave and an S wave. An R wave is the first positive deflection of the QRS... progression (large V1 and V2 with S waves in V4-V6) and right electrical axis deviationRight Axis Deviation - (more than +90 degrees): pulmonary hypertension, right ventricular hypertrophy, right bundle branch block, normal for children, high lateral MI Left Axis Deviation - (more negative than -30 degrees*): left ventricular hypertrophy, inferior MI, left bundle branch... are common findings with right ventricular hypertrophyAbnormal R wave progression can occur with acute myocardial infarctions and right ventricular hypertrophy. Large, dominant R waves in leads V1 and V2 may indicate posterior or lateral myocardial infarction and right ventricular hypertrophy. Poor R wave progression (i.e. not... (RVH). Similar to right atrial enlargementAtrial enlargement and dilation can be caused by tricuspid and bicuspid (mitral) valve disease, hypertension, and ventricular hypertrophy among other causes. A P wave can change with atrial enlargement to be taller than 2.5 mm in leads I, II and..., RVH occurs with lung disease and pulmonary valve dysfunction.
Left ventricular hypertrophy is reflected in taller than normal R waves in leads V5 and V6. One method involves adding the amplitude of the S waveAn S wave is the first wave after the R wave that dips below the baseline (isoelectric line). The end of the S wave occurs where the S wave begins to flatten out. This is called the J point. Figure... in lead V1 or V2 to the amplitude of the R wave in V5 or V6. If the amplitudes add to 35 mm or more, strongly suspect ventricular hypertrophy. Also, left ventricular hypertrophy may produce ST depression and T waveThe wave that arrives after the QRS; is a graphical presentation of ventricular repolarization. Expect a T wave to follow every QRS complex. The T wave is a graphic representation of the repolarization of the ventricle. The T wave is... inversion (ventricular strain) in the lateral leads V5 and V6.
Ventricular Strain
With severe ventricular hypertrophy, the myocardiumThe muscle layer of the heart; the middle layer that is responsible for contraction of the heart. The muscular myocardium is the thickest layer and the workhorse of the heart. It is composed of specialized muscle and electrical cells that... can thicken to such a degree that the blood supply to the subendocardium (inner lining of the heart just inside the endocardiumThe smooth innermost layer of the heart covers the inner chambers and the cardiac valves. The mechanical structures of the heart include the heart’s layers, chambers, septum, valves, and the major vessels (including the coronary arteries). Each of these structures...) can diminish. As a result, the endocardium is particularly susceptible to hypoxiaA sub-therapeutic blood oxygen level resulting in markedly reduced energy production and the formation of lactic and pyruvic acid (anaerobic metabolism). 1. Six Second ECG Guidebook (2012), T Barill, p. 197.
While uncomplicated ventricular hypertrophy affects ventricular depolarizationThe depolarization of the myocardium is represented on an ECG by a series of waveforms, one for atrial depolarization and soon after a larger waveform for ventricular depolarization. Normal ventricular depolarization begins with the septal fascicle of the left bundle... and the QRS complexA collection of waveforms (i.e. QRS complex and the ECG complex). 1. Six Second ECG Guidebook (2012), T Barill, p. 194 (i.e. tall R waves), severe ventricular hypertrophy can also affect ventricular repolarizationThe T wave is a graphic representation of the repolarization of the ventricle. The T wave is typically about 0.10 to 0.25 seconds wide with an amplitude less than 5 mm. While ventricular depolarization occurs rapidly producing a tall QRS... as seen with ischemic changes to the ST segmentA line between waves. Segments measure time between waves (waves are not included in a segment). While waves are fairly self-explanatory, intervals measure time from the start of one wave to the start of another wave (an interval includes at... and T wave. Called a ventricular strain patternPattern refers to the repeating components of an ECG rhythm in a predicative order. An ECG rhythm that is initiated by one of several intrinsic pacemaker sites of a heart will often generate a regular, even rhythm pattern. This can..., severe ventricular hypertrophy can cause ST segment depression and T wave inversion (see Figure 6.19).
Not surprisingly, a right ventricular strain pattern may be seen in leads closest to the right ventricleThe right ventricle ejects blood through the main branches of the left and right pulmonary arteries to the lungs. The chambers of the heart are the main drivers within an intricate pathway, delivering blood to the lungs for gas exchange... – leads V1 and V2. Left ventricular strain, if present, is usually evident in the lateral leads (I, aVL, V5 and V6).
As mentioned earlier, an echocardiogram should be ordered to prove or disprove 12 lead ECGElectrocardiogram; also called an EKG; a representation of electrical voltage measured across the chest over a period of time. 1. Six Second ECG Guidebook (2012), T Barill, p. 196 findings that only suggest possible hypertrophies. The value to being aware of these criteria includes the ability to recognize that ST depression and T wave inversion are not always signs of cardiac ischemiaThe ability to identify cardiac ischemia, injury and infarction is vital in the management of the majority of cardiac emergencies. Most sudden cardiac deaths are associated with an ischemic episode. Patient deaths due to an acute myocardial infarction (MI) typically.... After all, a 12 lead ECG is performed much more frequently than an echocardiogram. Evidence that supports chamber enlargement or hypertrophy could offer some insight into a patient’s current clinical status, prompting further investigations.
Figure 6.19 depicts the QRST ventricular strain pattern. Note the tall R wave that is typical of ventricular hypertrophy. A ventricular strain pattern includes ST depression and T wave inversion typically in leads with tall R waves.
1. Six Second ECG GuidebookA Practice Guide to Basic and 12 Lead ECG Interpretation, written by Tracy Barill, 2012 Introduction The ability to correctly interpret an electrocardiogram (ECG), be it a simple six second strip or a 12 lead ECG, is a vital skill... (2012), T Barill, p. 88, 154, 173-174