These findings suggest a limited applicability of these criteria in this subset of patients. The intraventricular conduction system is composed of the His-Purkinje system. Most of the previously described morphological criteria favoring ventricular tachycardia are present in a substantial percentage of patients with IVCD during sinus rhythm. The following criteria-QRS duration > 140 ms a left axis with right BBBM, right superior axis with right BBBM, monophasic or biphasic R wave in V1 with right BBBM, and a relation R/S 30 ms in lead V1 or V2 with left BBBM, > 60 ms from QRS onset to S nadir with left BBBM, a notched downstroke S wave with left BBBM, and an R-to-S interval > 100 ms in one precordial lead-had a specificity of 0.43, 0.54, 0.87, 0.80, 0.85, 0.78, 0.66, 0.69, and 0.63 (0.84 in right BBBM), respectively. The differential diagnosis of wide complex tachycardia also includes SVT with aberrancy or underlying bundle branch block and antegrade SVT conduction over an accessory pathway (antidromic SVT). Only 5 of 12 analyzed criteria had a specificity > or = 0.90 among our patients: (1) a triphasic configuration (Rsr' or Rr') QRS complex in V1 in the presence of a right bundle-branch block morphology (BBBM) (2) a QS, QR, or R QRS pattern in V6 in the presence of a right BBBM (3) any Q in V6 in the presence of a left BBBM (4) a concordant pattern in all precordial leads and (5) the absence of an RS complex in all precordial leads (particularly useful for left BBBM). The majority of wide complex tachycardias are secondary to VT. We analyzed prospectively the specificity of the QRS morphological criteria previously described in ECGs during sinus rhythm of 232 patients with IVCD. Abnormalities of local myocardial activation can further alter the specific pattern of venticular activation.
The specificity of previously described criteria in this context is unknown. An IVCD is the result of abnormal activation of the ventricles caused by conduction delay or block in one or more parts of the specialized conduction system (bundle of His, bundle branch or purkinje conduction system) resulting in widening of QRS complex. Although several ECG criteria have been described for the differential diagnosis of tachycardias with a wide QRS complex, their applicability in patients with preexisting intraventricular conduction defects (IVCDs) has been questioned. NOTE: If the patient has stable wide QRS tachycardia, consideration should be given to confirming the diagnosis of VT with adenosine.
0 kommentar(er)
