A wave that includes both an upright (positive) and downward (negative) deflection.
Expect a 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... More to follow every 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... More. The T wave is a graphic representation of the repolarizationFollows depolarization, involving the return to a pre-depolarization state; the myocardial cell’s electrical potential returns from +30 mV to its polarized state of –90 mV; the ions potassium, calcium and sodium are largely involved; note that contraction of the myocardial... More of the ventricle. The T wave is typically about 0.10 to 0.25 seconds wide with an 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 More less than 5 mm. While 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... More occurs rapidly producing a tall QRSThe 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... More complexA collection of waveforms (i.e. QRS complex and the ECG complex). 1. Six Second ECG Guidebook (2012), T Barill, p. 194 More, 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... More is spread over a longer intervalA period measured on rhythm strip paper that measures a wave and a segment; the distance measured is equal to time taken as an ECG is voltage over time; a PR interval for example is measured from the beginning of... More, resulting in a shorter and broader T wave.
The T wave is normally slightly asymmetrical and is usually larger than the P waveA wave generated from the depolarization of the atria; the P wave is upright when originating from the SA node. The P wave represents the depolarization of the right and left atria. The P wave begins with the first deviation... More (see Figure 4.13). The T wave is normally upright in lead II. Note that as heart rates increase, the P wave (atriaRight and left atria (1/3 volume and muscle mass of the ventricles) pump blood to the ventricles. Chambers and Layers of the Heart 1. Six Second ECG Guidebook (2012), T Barill, p. 190 More) and the T wave (ventriclesThe larger chambers of the heart (3 times the volume and muscle thickness than the atria), responsible for the pumping of blood to the lungs and the rest of the body. More) begin to share the same space on an 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 More. The larger T wave often covers the P wave. Note that the T wave is rarely notched. A notched T wave may also contain a P wave trying to show itself.
If ventricular repolarization returns cell membrane voltage back to its predepolarization resting electrical voltage, then shouldn’t the wave produced by ventricular repolarization be opposite that of ventricular depolarizationThe rapid influx of positive ions (sodium and/or calcium) into a cell – depolarization is necessary for contraction to occur. A depolarizing wave moves through the myocardium on average along a trajectory or vector. A vector is a force moving... More? In other words, should the QRS complex and the T wave face opposite directions,
upright and inverted. This is usually not the case.
Ventricular depolarization proceeds from 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... More to the epicardiumThe external layer that covers the heart – also called the visceral layer of the heart; between the visceral layer and the outer parietal layer is the pericardial sac; note that the coronary arteries travel along the epicardium before burrowing... More, essentially depolarizing the ventricles from the inside out. It follows that repolarization also occurs from the inside out, producing inverted T waves opposite in direction to the QRS complex. Instead, repolarization is delayed in endocardial cells, allowing the epicardium to repolarize first. Repolarization normally proceeds
opposite to depolarization, from the outside in. An upright T wave results.
An inverted T wave can point to 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... More among other causes. 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... More 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 of the epicardium, with repolarization now following the sequence of depolarization. An inverted T wave results.
Abnormally shaped T waves can signify acute episodes of cardiac ischemia, electrolyte imbalances, and the influence of cardiac medications. For example, peaked T waves can occur early during periods of myocardial ischemia and infarctionThe necrosis of tissue; acute myocardial infarction involves the acute death of myocardial cells. 1. Six Second ECG Guidebook (2012), T Barill, p. 198 More. Later, cardiac ischemia may cause the T wave to invert. Electrolyte imbalances can also affect the T wave. HyperkalemiaBlood potassium level higher than normal limits. Table 6.5 Normal and Abnormal Characteristics of ECG Waveforms Table 6.5 provides a non-exhaustive list of cardiac conditions that are associated with a variety of abnormal ECG waveforms. Arriving at a useful interpretation... More is often associated with peaked T waves. HypokalemiaBlood potassium level lower than normal limits. Table 6.5 Normal and Abnormal Characteristics of ECG Waveforms Table 6.5 provides a non-exhaustive list of cardiac conditions that are associated with a variety of abnormal ECG waveforms. Arriving at a useful interpretation... More can flatten the T wave. Quinidine can widen the T wave while digitalis can flatten the T wave.
Abnormally shaped T waves can also occur following injury to the lungs or the brain. While the physiology is not well understood, 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... More can occur with a leftsided tension pneumothorax. Peaked or inverted T waves have also been reported with brain injury, specifically subarachnoid hemorrhage.
Figure 4.13 depicts the component parts of the QRS complex…The 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... More begins at the J pointA small notch in the QRS where the ST segment begins. The point where the S Wave ends and begins to flatten out. Figure 4.13 The QRS Complex, ST Segment and the T Wave Figure 4.13 depicts the component parts... More and continues to the beginning of the T wave.
Figure 4.18 illustrates a variety of T waves, both normal and abnormal. A normal T wave is upright and slightly asymmetrical. During ischemic episodes, T waves may initially peak, then invert. Electrolyte imbalances such as hyperkalemia can cause the T wave to peak while hypokalemia is associated with flattened T waves. Certain medications such as quinidine can slow repolarization and widen the T wave while digoxin can flatten the T wave.
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... More (2012), T Barill, p. 88-90