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Cardiology Core Curriculum - part 5

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Nhịp tim nhanh này có thể bắt chước nhịp tim nhanh xoang trong làn sóng P là giống hệt nhau để nhìn thấy trong xoang nhịp. Không giống như nhịp tim nhanh xoang, nó là một nhịp điệu lại đăng ký dự thi bắt đầu và dừng lại đột ngột. | Cardiology Core Curriculum Sinus nodal re-entrant tachycardia This tachycardia can mimic sinus tachycardia in that the P wave is identical to that seen during sinus rhythm. Unlike sinus tachycardia it is a re-entrant rhythm that starts and stops abruptly. The symptoms are similar to those seen with atrial tachycardia. Treatment with P-blockers and calcium channel blockers can reduce the recurrence of the rhythm and radiofrequency catheter ablation may offer a cure. Atrioventricular nodal re-entrant tachycardia AV nodal re-entrant tachycardia AVNRT is responsible for approximately 60 cases of paroxysmal supraventricular tachycardia PSVT also referred to as PAT and SVT . These arrhythmias have a narrow QRS complex paroxysmal onset and termination and ventricular rates between 150 and 250 beat min Table 8.2 . In the typical form of AVNRT the electrical impulse travels down the slow pathway of the AV node and re-enters back up the fast pathway. This results in a tachycardia with P waves that are either buried within or occur just before or after the QRS complex. An R in electrocardiogram lead V1 that is only present during tachycardia represents the superimposed P wave and is diagnostic Figure 8.4 . In the atypical form of AVNRT 5 the re-entry circuit is reversed down the fast and back up the slow and the P wave occurs substantially after the QRS so-called long RP tachycardia . AVNRT occurs in structurally normal hearts with a slight preponderance in women and increases in incidence with age. Clinically the patient presents with palpitations breathlessness and neck pounding. There may be no precipitating factor. Presyncope and syncope are uncommon but may occur early following onset. AVNRT may be terminated using vagal maneuvers such as carotid massage and Valsalva these techniques yield transient block in the slow pathway of the AV node and terminate re-entry. Adenosine an endogenous nucleoside represents the best drug option for conversion to sinus rhythm and is .