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EKG 3. Supraventricular Tachycardia . “Supraventricular” imparts the understanding that all atrial foci and all junctional foci are above the ventricles. Page 153 Rate 150-250. Right Bundle Branch Block. Caused by a block in the Right Bundle Branch. Delays depolarization. Page 191
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Supraventricular Tachycardia • “Supraventricular” imparts the understanding that all atrial foci and all junctional foci are above the ventricles. • Page 153 • Rate 150-250
Right Bundle Branch Block • Caused by a block in the Right Bundle Branch. Delays depolarization. Page 191 • Ordinarily both ventricles are depolarized simultaneously. • Therefore, causing two joined QRS’s • Usually see two R Waves (R & R1) • QRS > .12 seconds
BBB Cont. • In LBBB, Left Ventricular depolarization is delayed • In RBBB, Right Ventricular depolarization is delayed (Page 194) • If BBB is suspected check V1 & V2 (Right Chest Leads) & leads V5 & V6 (Left Chest Leads) for the R,R1 • Usually the rate is tachycardia
Left Bundle Branch Block • LBBB has two subdivisions; called Hemiblocks • These are often referred to as “bunny ears” • LBBB and RBBB can be diagnosed by appearance alone • LBBB on GXT typically termination of test due to diagnosis data
Infarction • Myocardial Infarction - Complete occlusion of the coronary artery • The infarcted area becomes necrotic (dead), so it can’t contract • The EKG can tell us which coronary branch is occluded • We may also be able to detect a narrowed vessel.
Infarction (cont.) • Most critical infarcts originate in the left ventricle (Page 259 - ) • Myocardial Triad - Ischemia, Injury, Necrosis • The word hypoxia means decreased oxygen; in the heart it is usually caused by ischemia, which means reduced blood supply.
Infarction (cont.) • Ischemia is characterized by inverted T Waves • Cardiac ischemia alone can cause chest pain known as angina, which is usually associated with T Wave inversion. • T Wave inversion in leads V2-V6 is considered pathological. Marked T Wave inversion in V2 & V3 alerts to stenosis of anterior descending coronary (p. 265)
Infarction (cont.) • Injury indicates the acuteness of the infart. Elevation of the ST segment denotes “injury”. • Slight elevation or as much as 10 mm • Earliest consistent sign of an infarction to record on EKG. • Angina w/ exertion, Prinzmetal’s angina, can cause ST elevation in the absence of MI
Infarction (cont.) • If ST segment is elevated without associated Q Waves, this may represent non-Q Wave infarction. • The infarction maybe old or new. It is important to make that distinction.
ST Segment Depression • During angina, ST segments may become temporarily depressed. • A subendocardial infarction will depress the ST segment. • During a stress test, a pt with narrowed arteries demands more blood flow than the arteries can deliver, produces ST depression
ST Depression (cont.) • Digitalis can cause ST segment depression w/ a unique appearance p. 270, 317 • Subendocardial infarction causes flat depression of the ST segment (p 271) • The above is a form of Non-Q wave MI. • Any pt with acute ST depression should have an immediate workup
Infarction (cont.) • Q Waves in V1, V2, V3, or V4 signify an interior infarction • Q Waves in the lateral leads, I and AVL represent a lateral MI • Q Waves in the inferior leads; II, III, and AVF can represent inferior MI • Acute Anterior MI - Page 283
Infarction (cont.) • Acute Posterior Infarction - Large R Wave (the opposite of a Q wave ) in V1 and V2 • ST depression in V1 or V2 • Page 285-286 • Page 291
Electrolyte Problems • Elevated serum Potassium levels • The P wave flattens down, the QRS complex widens, and the T Wave becomes peaked • Hyperkalemia - QRS widens • Hypokalemia - T Wave flattens out and may invert (page 315) • K plays important role in depolarization
Electrolyte (cont.) • Elevated Ca levels accelerate both ventricular depolarization and repolarization • Short QT interval
Digatalis Effect • Digatalis causes a gradual downward curve of the ST segment. Page 317 • Digatalis slows the SA Node pacing rate • Tends to cause AV Blocks or even Sinus Blocks • Digatalis Toxicity - Atrial and Junc. Tachy-arrhythmias, PVC’s, Vfib, Vtach, Bigeminy
COPD and EKG’s • COPD often produces low voltage amplitude in all leads • The Rt Ventricle works against considerable resistance so there is usually some degree of Rt Ventricular Hypertrophy • Atrial Tachycardia seen often
Pacemakers • Implanted artificial PM • Originally developed for brady rhythms • Paced electrical stimulus “captures” the myocardial tissue and contracts • Page 322 • If resumes normal rate it will cease pacing • Page 324
Heart Transplant • Heart Transplant procedure leaves portions of patient’s native atria in place. • So the transplant patient has portions of their native SA Node and the donors. • Two SA Nodes • Two P Waves