Cardiology In Critical Care
Ventricular Tachycardia (Vtach, VT)
Impulses originating in the SA node control the atria but fail to reach the ventricles; the latter are activated by their own pacemaker firing 100-250/min; rarely ventricle-borne impulses are also conducted to the atria. P waves are frequently indiscernible or may appear as notches at various points on the QRS-T complexes; if P waves are recognizable, they are usually of normal configuration, occur regularly at a rate 60-100 and bear no fixed relation to the QRS complexes (AV dissociation). Rarely, when the atria are controlled by the ventricular pacemaker, the P waves are inverted and follow QRS complexes at a constant RP interval. When the rate is less than 150, the SA-borne impulse may be occasionally conducted through the AV junction and it can activate the ventricles thus producing a QRS complex whose configuration and width are intermediate between the normal and abnormal complexes (fusion beat or partial capture). QRS complexes are usually wider than 0.12 sec and bizarre. RR intervals are usually regular but may vary up to 0.03 sec. Vagal stimulation has no effect on the rate. An ECG prior to tachycardia showing premature beats of identical configuration favors ventricular origin of the tachycardia.
A. Definition -- a run of three (3) or more
1. Three or more consecutive bizarre, premature beats, each with 1 width of at least 0.12 seconds and the
T wave in the opposite direction fiom the QRS.
2. Ventricular rate 100-250/min.
3. Rhythm is essentially regular, but may vary slightly.
4. May occur as a single isolated basf may recur paroxsysmally or may persist for a long run.
C. Clinical Significance
1. Usually indicative of significant underlying cardiovascular disease.
2. Most patients are not able to maintain an adequate blood pressure with persistent V-tach and will quickly become hypotensive.
3. V-tach often degenerates into Ventricular Fibrillation. (V-Fib, VF).
1. Prevention - treat malignant PVCs before V-tach develops.
2. Hemodynamicallv stable - (Normal B/P, No chest pain)
a. Lidocane 1mg/kg. IV bolus (May give precordial thump).
b. Lidocaine 1 - 1.5mgkg. every 8 minutes until V-tach resolves or up to 3mg/kg. has been given.
c. If V-tach persists give Procainamide, 20 mg/min. Until V-taeh resolves or up to 17mg/kg. has been given.
d. If V-tach persists, cardiovert as in unstable patients.
e. After normal rhythm is restored, the patient should remain on antiarrhythmic infusion, until stable.
3. Hemodvnamicallv unstable -
a. Check oxygen saturation, IV access, Consider sedation. Have suction and intubation equipment available.
b. Cardiovert with 100 joules.
c. Cardiovert with 200 joules.
d. Cardiovert with 300joules.
e. Cardiovert with up to 360 joules.
f. If recurrent, add Lidocaine and Cardiovert at starting level. If unsuccessful then procainamide or bretylium.
4. Pulseless V-tach - treat a V-fib.
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