![]() ![]() ![]() Procainamide leads to initial 2: 1 blockage and later complete block of conduction over accessory pathway, and pseudo-infarction pattern of posterior inferior MI type disappeared. mentioned the intravenous use of procainamide to differentiate between the myocardial infarction and WPW in a similar situation. However, the presence of T wave inversion with inferior Q waves and a normal PR interval (referred to as Q wave-T wave concordance) was strongly suggestive of inferior ischemia, and further evaluation (echocardiogram) for infarction was warranted. This characteristic Q wave-T wave vector discordance results from secondary repolarization changes due to altered ventricular activation. The pseudo-infarct Q waves in the inferior leads were associated with a short PR and positive T waves (known as Q wave-T wave discordance). In our patient, because of the left inferoseptal location of the accessory pathway, the ventricles were activated posteriorly and inferiorly first, then down to up, in a reverse sequence compared to physiologic activation and therefore generated negative forces on the ECG in the form of a Q wave in inferior leads. It can also mask true infarction, as in our case. The picture becomes further convoluted as WPW itself can also alter both depolarization and repolarization and can mimic acute infarctions. Myocardial infarction and myocardial ischemia can affect the electrophysiologic characteristics of normal AV conduction system, and can lead to changes in QRS morphology, AV node prolongation, new Q waves, and changes in the ST segments or T wave. The AV bypass tract conducts faster than the normally-located AV nodal pathways, resulting in early excitation of the ventricle connected to the accessory pathways. Although the WPW pattern is more prevalent than the syndrome, both are relatively rare in the general population (the prevalence of WPW syndrome in the general population is 0.1 to 3. The WPW pattern is the pre-excitation findings in sinus rhythm on the ECG in the absence of symptomatic arrhythmias, whereas the WPW syndrome is the pre-excitation findings in the setting of symptomatic arrhythmias. This constellation of ECG findings is known as the pseudo-infarct pattern. Wolff-Parkinson-White is a pre-excitation syndrome with a symptomatic accessory pathway leading to characteristic ECG changes in sinus rhythm of short PR interval, the presence of delta waves, wide QRS complexes, and potentially Q wave-T wave vector discordance. The patient was then started on the guideline-directed medical therapy (aspirin, metoprolol, statin, and angiotensin-converting enzyme inhibitor). The patient underwent a nuclear stress test that showed a limited fixed defect in the inferior left ventricle without signs of ischemia in the rest of the myocardium and an ejection fraction of 50%. As persistent Q waves were highly suggestive of an old infarction, a 2D echocardiogram was done, which confirmed wall motion abnormality and an old inferior wall myocardial infarction (wall thin and akinetic) that was masked on the surface ECG by the ventricular pre-excitation. However, instead of the positive and narrower QRS complexes in inferior leads typically expected after elimination of such accessory pathways, the ECG showed a narrower Q wave in inferior leads ( Figure 2). The native conduction through the physiologic His-Purkinje system showed a PR interval longer than 0.2 s (first-degree atrioventricular block). After successful radiofrequency ablation of a left inferoseptal accessory pathway, the pre-excitation pattern (short PR and delta wave) disappeared. Since the patient was experiencing a significant amount of SVT refractory to medications (recorded on a Holter monitor), the patient underwent an electrophysiology study and ablation of his accessory pathway. A 61-year-old diabetic man with a history of recurrent palpitations was found to have supra-ventricular tachycardias (SVT) on the ECG, with the typical characteristic of a Wolff-Parkinson-White pattern (short PR interval of 0.10 s. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |