Ventricular Rhythms PDF

Caused by catecholamines, stimulants,...

Caused by catecholamines, stimulants, digoxin toxicity, hypoxia, and acute Enhanced automaticity myocardial infarction (AMI) Disorders of Impulse Generation Sinus exit block, sinus arrest, failure of AV Decreased automaticity of primary junction backup pacemaker, complete pacemakers (SA/AV node) heart block Mechanisms of Ventricular Rhythms Re-entry is the likely mechanism responsible for the majority of clinically significant tachycardias A zone of tissue that conducts slowly Disorders of Impulse Conduction (short refractory period) and a zone that conducts quickly (long refractory period) Conditions required for re-entrant tachycardias include: Conduction velocity slow enough to allow the tissue at the beginning of the circuit to recover Originate in the ventricles, occur earlier Only treat if symptomatic than the expected next beat, and have a compensatory pause Avoid stimulants (caffeine, alcohol, catecholamines, environmental stress) In healthy hearts, PVCs do not increase the risk of sudden cardiac death, but in Correct reversible causes (electrolyte heart disease, they can increase the risk abnormalities, hypoxia, acidosis) and lead to more serious rhythms Treatment of PVCs Use beta-blockers, especially post-MI Causes of PVCs include electrolyte Premature Ventricular imbalances, metabolic acidosis, hypoxia, myocardial ischemia, ventricular Amiodarone IV can be used acutely Complexes (PVCs) hypertrophy, antiarrhythmic drugs, sympathomimetic drugs, infection, excessive alcohol intake, and stimulants A combination of beta-blockers and amiodarone can be safely administered to high-risk patients Types of PVCs include unifocal (same ectopic focus) and multifocal (different ectopic foci) Bigeminy (every second beat is a PVC) and trigeminy (every third beat is a PVC) are concerning patterns Occurs when a PVC "lands" on the T wave of a QRS complex R on T Phenomenon This can be significant and lead to ventricular tachycardia or fibrillation Ventricular escape beats occur when the SA node fails, and the backup pacemaker in the AV junction also fails, leading a slow ventricular focus to take over Ventricular escape rhythm occurs when there are three or more ventricular escape beats in a row Consists of three or more consecutive ventricular beats with a rate of 40-100 bpm Characteristics include a regular rhythm, rate of 20-40 bpm, wide and bizarre QRS, and T waves of opposite polarity to the The sinus and ventricular pacemakers QRS Accelerated Idioventricular Rhythm (AIVR) compete for dominance ECG characteristics include a usually Ventricular regular rhythm, gradual onset and termination, wide and bizarre QRS, and T Rhythms: waves of opposite polarity to the QRS Mechanisms, Ventricular escape can cause palpitations, Disorders, and decreased cardiac output and blood pressure, dizziness, syncope, confusion, Treatment- If symptomatic follow the ARC Management breathlessness, and decreased urine output bradycardia algorithm A potentially life-threatening rhythm that requires immediate attention Sustained for more than 30 seconds, with a Determined by the rate and the degree of heart rate of 110-250 bpm, a regular left ventricular dysfunction rhythm, and wide and bizarre QRS complexes Hemodynamic Compromise in VT Rapid rate decreases ventricular filling time, and AV dissociation and loss of atrial kick can worsen hemodynamics Ventricular Tachycardia (VT) Mechanism is often re-entry, often due to scar tissue from a previous myocardial infarction Most common causes are ischemic heart disease (MI or acute ischemia, prior MI, post-reperfusion), followed by dilated and hypertrophic cardiomyopathy, and other causes like electrolyte abnormalities, mechanical stimulation, and digoxin toxicity A polymorphic form of ventricular tachycardia resulting from prolonged ventricular repolarization (long QT) Address the underlying cause Discontinue any drugs that prolong the QT interval Amiodarone Initiated when a PVC occurs during the preceding T wave (relative refractory period)‘ R on T phenomenon Treatment of Torsades de Pointes Administer IV magnesium and potassium Torsades de Pointes (TdP) Consider atrial or ventricular overdrive pacing Avoid inotropes as they can be proarrhythmic Causes include acquired factors (drug- induced, electrolyte abnormalities, bradycardia, CVA, starvation) and congenital long QT syndrome Requires immediate intervention with defibrillation Causes include ischemic heart disease, myocardial infarction, VT, R on T Ventricular Fibrillation (VF) phenomenon, electrolyte disturbances, acid-base imbalance, hypothermia, cardiomyopathy, myocarditis, drug toxicities, Brugada syndrome, long QT, and Wolff-Parkinson-White syndrome