A wide 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... that arrives early is called a premature ventricular complexA collection of waveforms (i.e. QRS complex and the ECG complex). 1. Six Second ECG Guidebook (2012), T Barill, p. 194 (PVC). A PVC has a width of 0.12 seconds or longer. The elongated period of 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... is caused by an abnormal, less efficient pathway 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.... The resulting ventricular contraction results in a weaker contraction and reduced stroke volumeThe amount of blood ejected by either the right or left ventricle with one beat (contraction). While heart rate is an undisputed contributor to cardiac output, stroke volume is the other major player. As heart rates vary to changes in.... PVCs come in different categories: unifocal (coming from the same location), multifocal (coming from different locations), in pairs (ventricular couplets), and non-sustained groups of 3 or more (runs, bursts, or salvos).
Heart rateThe number of QRS complexes per minute; note that HR may not equal perfused pulse rate. See also: - Step 1 Heart Rate - Rate - Rule of 300s (Triplicate Method) - Six Second Count - The Caliper Method 1.... is the number of QRS complexes – the number of ventricular depolarizations – present in a minute. Heart rateHeart Rate; calculated by counting the number of QRS complexes in six seconds and multiplying by 10; rate is also determined by measuring the number of large squares between two R waves; i.e. –1 large square = heart rate of 300/minute. is not always the same as pulse. Heart rate is a measurement of electrical activity while pulse ensures the perfusion of the blood to the target tissues.
Many have been caught depending on the cardiac monitor for vital information such as heart rate. For example, patients with electronic pacemakers may display heart rates twice the pulse rateHeart rate is not always the same as pulse. Heart rate is a measurement of electrical activity while pulse ensures the perfusion of the blood to the target tissues. Many have been caught depending on the cardiac monitor for vital.... This occurs because the QRS complex produced after the pacer spikeThe telling sign that the rhythm is a paced rhythm; since the pacemaker spike is vertical, virtually no time was spent – this suggests strongly that the spike was initiated artificially and not organically (within the heart); note that a... also may count as a separate QRS complex, thus doubling the heart rate.
Another example of a serious disparity between heart rate and pulse occurs with premature ventricular complexes (called PVCs). The PVCs come early and cause short filling times. It follows then that the 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. stretch minimally and subsequently contract ineffectively. The outcome: many PVCs fail to produce a perfusing pulse and the peripheral pulse is less than the heart rate displayed by the cardiac monitor (which includes both normal QRS complexes and PVC complexes).
The patient – not the monitor – is the gold standard.
This cannot be said enough. Most of us have been caught at one time or another relying on the cardiac monitor to the exclusion and great risk of the patient.
Heart rate is virtually always provided on the screen of a cardiac monitor. This number may offer some value but taking a patient’s pulse is always good practice. Don’t get burned.
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. 91, 118, 203