List the 6 ventricular arrhythmias: V3PAT
1. Ventricular tachycardia 2. Ventricular Flutter; 3. Ventricular Fibrillation; 4. Premature ventricular contractions; 5. Accelerated Idioventricular rhythm 6. Torsades de Pointes
Characteristics of Premature ventricular contrations (PVC) aka ventricular premature beat (VPB):
Most common ventricular arrhythmia (can be normal); EKG: occur before the next normal beat is expected (hence premature), QRS is wide and bizzarre; usually no p wave (if present, points in opposite direction of QRS); compensatory long pause. Can trigger life threatening arrhythmias in acute myocardial infarction. Ventricular Bigeminy-one normal sinus beat to one PVC; trigeminy: two normal sinus beat for every one PVC; morphology depends on where the beat originate and can be uniform or multiform.
PVC and Benign/stable vs. presence of organic heart disease:
PVCs may be stable or benign if caused by: 1. caffeine 2. anxiety, 3. drugs: epinephrine, isoproterenol, aminophyline; PVCs may indicate the presence of organic heart disease: 1. valvular disease; 2. HTN; 3. Ischemia 4. Electrolyte imbalance (image heart if frequent PVCs)
*When should you worry about PVCs; Rules of malignancy of PVCs: 5
1. Frequent PVCs; 2. Runs of consecutive PVCs, especially three or more in a row. 3. Multiform PVCs, in which PVCs vary in their site of origin (have different shapes). 4. PVCs fallling on the T wave, "R on T" phenomenon-may precipitate abnormal rhythm like ventricular tachycardia). 5. Any PVC in acute myocardial infarction.
Characteristics of ventricular Tachycardia
A run of three or more consecutive PVCs, d/t reentrant. Rate: 120-200 bpm. May be slightly irregular. If sustained, can be an emergency b/c pt becomes hypotensive, may degenerate into ventricular fibrillation.
Uniform/monomorphic vs polymorphic ventricular tachycardia.
a. Uniform/monomorphic if d/t to healed infarctions. b. polymorphic if d/t: 1. acute coronary ischemia; 2. acute infraction, 3. Profound electrolyte disturbances;4. prolongation of QT interval.
Characteristics of Ventricular Flutter
Very rapid ventricular tachycardia; EKG: sine wave appearance, with similar amplitude; d/t reentrant. Rate: 250-350 bpm; Prelude to ventricular fibrillation.
Characteristics of Ventricular fibrillation
Preterminal event seen in dying hearts. d/t reentrant. EKG: Chaotic, appear coarse and fine. No true QRS complexes; No cardiac output. Unconsciousness. Tx: CPR and Electrical defibrillation.
Characteristics: Accelerated Idioventricular Rhythm
Benign rhythm; Rate: 50-100 bpm; Wide QRS with no p wave.; seen during acute infarction or in reperfusion; If rate if below 50 bpm=Idioventricular rhythm.
Characteristics of Torsades de Pointes
Seen in pt with prolonged QT intervals. A unique form of ventricular tachycardia--polymorphic VT. EKG: direction of QRS complexes appears to spiral around a baseline.
Causes of Prolonged QT interval, and hence Torsades de Pointes
1. congenital, 2. electrolyte imbalances (hypo ca, mg, k) 3. acute myocardial infarction; 4. drugs: antiarrhythmics; tricyclic antidepressants, phenothiazines, antimigraine, antifungal medications, antihistamines (diphenhydramine), antibiotics.
Antibiotics that causes prolonged QT interval:
Erythromycin, quinolones, trimethroprim, pentamindine
Antimigraine that cause prolonged QT interval:
Naratriptan; zolmitriptan, Sumatriptan
Antifungal medications that causes prolonged Qt intervals:
Ketoconazole, fluconazole, Itraconazole
Atrial premature beat that occurs so early that the Purkinjie fibers have not had a chance to repolarize fully. So that depolarization appear sluggish with wide, bizarre QRS complex like a PVC. (but usually no P wave with PVC)
Differentiate b/w supraventricular and ventricular arrhythmias--if only isolate beats
1. No P wave, the its ventricular=PVC; if p wave present= supraventricular.
differentiate b/w Supraventricular vs. ventricular arrhythmias in multiple consecutive beats--use clinical clues.
1. Is it a diseased heart--if diseased then ventricular; if healthy then supraventricular. 2. Effect of carotid massage: Carotid massage terminate for supraventricular but not for ventricular arrhythmias. 3. Look for cannon A waves of AV dissociation in JVP--seen in ventricular arryhtmias.
differentiate b/w Supraventricular vs. ventricular arrhythmias in multiple consecutive beats--use electrocardiographic clues.
Look for p waves: 1:1 relationship in PSVTA; p wave and QRS unrelated in VT. Fusion beats in VT only (a beat midway b/w normal sinus beat and PVC). Initial deflection- same as QRS in PSVTA, but opposite of QRS deflection in VT. QRS duration of greater than 0.14 is VT.
Seen in atrial fibrillation pt. See a wide aberrantly conducted supraventricular beat occuring after a QRS complex that is preceded by a long pause. See a bizarre wide QRS.
Programmed electrical stimulation--EPS: electrophysiologic studies
Useful for pt with recurrent VT. Serves to map the arryhtmia. Transvenous catheters are placed. Then arrhythmia is induced and recorded. Catherer ablation may accompany procedure to ablate a portion of reenterant pathway-->permanent cure
Implantable vs. External defibrillator
Implantable: similar to a pacemaker, when dangerous arrhythmia is detected, electric shock is delivered. Automated external defibrillator (AED): detects rhythm, may deliver shock.