ECG (EKG) Flashcards
pathways that the AP follows in the atria
Bachmann’s bundle and inter-nodal pathways p. 277
conduction velocity through the AV node is…
slower, allowing a delay between atrial and ventricular contractions p. 277
normal ECG speed and deflection
25mm/sec and 10mm = 1mV p. 279
rates of normal and latent pacemakers
SA node 60-80 bpm
AV node 40 bpm
ventricular muscle 30 bpm
p.282
reentry conduction
an abnormal circuit in the heart; must have a barrier, a unidirectional block and conduction time has to exceed the effective refractory period p283-4
fibrillation
random chaotic wavefronts move through the atria or ventricles causing there to be no effective pumping action :”bag of worms”
heart failure
symptom complex (syndrome) that is normally secondary to cardiac (myocardial) failure; def: the heart is unable to meet the metabolic requirements of the peripheral tissues p.286
heart failure stats
1-2% of general population; over 65 6-10%; #1 discharge diagnosis of Medicare; $20-40B spent annually p.286
2 types of heart failure
systolic dysfunction and diastolic dysfunction; systolic dysfunction is when the heart cannot pump enough out via the ventricles; diastolic dysfunction causes there to be abnormal relaxation of the ventricles, ‘stiff ventricle’ p. 287
4 stages of heart failure
Three categories to meet: risk factors, structural disease and symptoms. Four risk factors are A, B, C, and D. A is least, only risk factors. D is worst with all three categories met and the symptoms being severe. p.287
how to measure preload
catheter in the LV, or wedge pressure (cath in the pulmonary artery); wedge pressure only works in the absence of mitral stenosis p. 287
preload determines
the force of cardiac contraction (in a healthy heart)
afterload is measured by…
SVR or aortic pressure
contractility units
change in pressure over change in time (mmHg/sec) p.288
heart failure can arise because of…
low preload (hypovolumic, constrictive pericarditis, tricuspid stenosis) high afterload (aortic stenosis, hypertension) impaired contractility (prior infarction, familial cardiomyopathy, infiltrative disease) Low HR (bradyarrhythmia) p.288
heart failure (circulatory failure)
circulatory failure in the presence of a functioning heart secondary to hypothyroidism, beriberi, arteriovenous shunt, anemia p. 288
treatments for heart failure
increase preload, increase contractility, decrease afterload
abnormal Ca metabolism leads to
genetic reprogramming of the myocyte
neurohumoral activation including
sympathetic innervation; renin-angiotensin-aldosterone system to raise Na retention and cause peripheral vasoconstriction p.290
Kidney’s retain Na; effects?
raises the fluid levels in the body to the point that there is congestion in the lungs, edema, ascites, hepatomegaly (increases preload) p. 290
renin-angiotensin system and sympathetic system kick in during CHF: effects?
raises afterload, which only exacerbates the problem by increasing the demand for O2 by raising contraction rate
CHF causes HR to rise: effects?
increased demand for O2, with a 1:1 correlation in the rate of BPM to O2 demand p.290
treatment for CHF involves…
knocking out the body’s own compensatory mechanisms: kidney Na retention: diuretics, renin-angiotensin/sympathetics - vasodilators: heart rate increases… not sure on this one…
higher LVEDP pressures lead to…
pulmonary edema, when the filling pressure exceeds the oncotic pressure in the capillaries p. 290
