Cardiology In Critical Care
Lethal Dysrhythmias of the Heart
Premature Ventricular Complexes (PVCs)
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Premature Ventricular Complexes (PVCs)
A. Etiology -- an irritable focus in the
ventricle discharges before the arrival of the next anticipated
impulse from the sinus node.
Because the impulse arises in either the right or the left
ventricle it does not travel down the normz;l conduction pathway
(normally
the right and left ventricles are depolarized simultaneously).
This produces an abnormal, bizarre-looking complex.
B. Characteristics
1. Premature, occurring before & next expected beat.
2. No P wave before the PVC.
3. Compensatory pause
4. QRS widened (0.12 or wider)
5. T wave is usually oppositely directed from QRS complex.
C. Clinical significance
1. May be a stable, benign finding in many patients
2. May be a precursor to other more dangerous dysrhvthmias.
3. Patient may feel "palpitations".
4. May lose significant amount of stroke volume with PVCs, precipitating angina, hypotension.
D. When to treat PVCs
1. When they Occur at the rate of greater than 6 per minute.
2. Multifocal PVCs
3. R - on - T PVCs
4. Bigeminy PVCs (every other beat is a PVC)
5. Runs of two (2) or more PVCs in a row.
E. Treatment
1. Determine the underlying cause
a. rnyocardial ischemia
b. hypoxemia
c. digitalis toxicity, epinephrine, aminophyline
d. hypokalemia
e. anemia
f. CHF
g. fever
h. acidosis
i. bradycardia
j. anxiety
k.caffeine2. Treatment
a. If PVCs are occurring with bradycardia or AV block, it may help to speed up the heart rate with Atropine
b. Treat the underlying cause.
c. Lidocaine IV
1. Initial IV bolus of 1 - 1.5 mg/kg.
2. If not suppressed, repeat hdocaine, 0.5 - 1.5mg/kg, until no
ectopy, or up to 3mg/kg is given.3. Once ectopy is resolved, follow by an infusion of 2 Gm. in
500cc D5W to infuse at 1-4 mg/min.4. If patient continues to have PVCs, the drip rate may be increased (up to 4mg/min), but only after repeating thebolus agin (Do Not exceed 400-500 mg/hr).
5. Onset of action is 45-90 seconds and the duration of action is 10-20 minutes.6. Primarily metabolized by the hver; very little excreted by
kidneys.
7. Side effects: drowsiness, disorientation, decreased hearing ability, parathesias, muscle twitching, grand mal seizures.d. Procainamide
1. Used primarily when hdocaine has been ineffective.
2. Bolus with too mg. every 5 minutes at a rate of 20-30 mg/min. until:
a) dysrhytbmia is suppressed
b) patient becomes hypotensive
c) QRS is widened by 50
d) Until 17 mg/kg has been given
3. Maintenance infusion of I-4mg/min.
4. Precautions - hypotension, widened QRS, lengthened PR or QT interval, AV blocks
e. Bretyhum
1. Used when lidocaine and procainamide are ineffective.
2. Give 5-10mg/kg. over 8-10 minutes.
3. Maintenance infusion: 500 mg. in 250 or 500cc DSW infuse
at a rate of 1-2 mg/min.4. Side effects: Initial rise in heart rate and BP, Postural hypotension, nausea and oomiting, if given too rapidly.
