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.... and contractilityA muscle cell’s ability to shorten or contract through the action of actin and myosin - mediated by the calcium ion; the faster the influx of calcium, the more forceful the contraction. 1. Six Second ECG Guidebook (2012), T Barill, p. 194 are influenced by sympathetic innervation of the heart. Sympathetic innervation which releases epinephrine and norepinephrine, influences cardiac outputWhat is it? Why is it Vital? The amount of blood pumped out of the ventricle in a minute (most often refers to the blood pumped by the left ventricle) What is cardiac output? Simply, cardiac output is the amount... through its alpha effect (peripheral vasoconstriction) and its beta 1 effect (increases 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. and force of contraction). The alpha effect provides more preloadTechnically the end-diastolic pressure of either the left or right ventricles; simplified as the blood volume supplied to the left or right ventricles; note that the more volume or preload, the greater the myocardial stretch and forceful the contraction; increased... by shunting blood to the core organs (including the heart). While the alpha effect can also increase afterloadThe pressure that the ventricle (right or left) must overcome to eject blood (i.e. the left ventricle pumps against aortic diastolic pressure and systemic vascular resistance. The resistance to the ejection of blood by the ventricle is called afterload. The..., sympathetic stimulationIschemia and sympathetic stimulation can enhance a ventricle’s automaticity, stimulating the ventricle to initiate an impulse before a sinus initiated wave reaches the ventricles. This solitary wave doesn’t ride the Autobahn. Rather, this one wave must traverse both ventricles. The... usually boosts cardiac output.
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. 36