AV Block and Ventricular Arrhythmias Flashcards
What are the characteristics of first degree AV block?
Normal P wave
Prolonged PR interval
Normal QRS complex and rest of conduction
What is another name for first degree AV block?
Prolonged AV conduction
Define second degree AV block
Some atrial impulses fail to conduct to the ventricles (lonely P wave)
What are the two types of second degree AV block?
Mobitz type I (Wenkebach - physiologic)
Mobitz type II (pathologic)
How can Mobitz type I be distinguished from Mobitz type II second degree AV block?
Type I 2:1 conduction Asymptomatic Associated with high vagal tone Responds to atropine Will speed and slow based sympathetic and parasympathetic innervation Remove underlying cause to treat
Type II >2:1 conduction Symptoms vary based on degree of block Structural dz of AV node often present Partially responsive to atropine May require pacemaker
How is the Atropine response test conducted?
.04 mg/kg IV, wait 5-10 min for response (usually sooner); if HR >180 without further block, secondary to high vagal tone; if HR not >180 or persistent block, AV nodal dz, pacemaker needed
What is third degree AV block?
Complete failure of AV node conducion
Some part of conduction system must take over as pacemaker
How does level of block in third degree AV block affect ECG readout?
If at AV node, junctional escapes with narrow QRS complexes will be present
If at His-purkinje level, ventricular escapes with wide QRS complexes
What are some clinical signs associated with third degree AV block?
Collapse or fainting Heart failure (left or right sided) GI signs, weakness, lethargy, azotemia (loss of forward flow)
How is third degree AV block treated?
Pacemaker
Isoproterenol IV infusion
What is an ectopic beat?
One that arises from an area other than the SA node; can be early or late
What is a Premature venticular complex (PVC)?
It is a conduction that has a much wider QRS wave and overall different appearance from sinus conduction
What is bigeminy?
Each normal conduction is followed by an abnormal one; may be atrial or ventricular
What is a fusion beat?
Combination of supraventricular (sinus) complex and PVC
What are some causes of VPCs?
Primary cardiac disease Metabolic/Endocrine disorders Drugs/Toxins (Digoxin, Amphetamine, Theobromine) GDV Sepsis Splenic disease Hypoxia Hypovolemia Pain Trauma Autonomic imbalance (increased sympathetic)
What is accelerated idioventricular rhythm?
Pts who are septic, hypovolemic, etc. go between sinus and ventricular arrhythmia
How are PVCs treated?
Address the underlying disease
Lidocaine (1B) or procainamide (1A)
What does sustained ventricular tachycardia look like on an ECG strip?
Wide, saw tooth pattern (ventricular flutter)
In what instances would you see sustained ventricular tachycardia?
Boxers with arrhythmogenic right ventricular cardiomyopathy
Doberman with dilated cardiomyopathy
Myocarditis (Chagas dz)
What are some hemodynamic consequences of arrhythmias?
Decreased cardiac function Drop in blood pressure Reduced tissue perfusion Limited exercise capacity Syncope
What are some electrical instability consequences of arrhythmias?
Myocardial fibrillation
Asystole
Sudden cardiac death
How is ventricular fibrillation treated?
Defibrillation
Magnesium (.2mEq/kg IV)
What drugs are available for treatment of ventricular dysrhytmia?
Lidocaine Procainamide Amiodarone Magnesium salts Quinidine NG Phenytoin Direct current cardioversion
At home: Sotalol Procainamide Amiodarone Atenolol Mexilitine
