3. Causes of Syncope

4. Age-Dependent Causes of Syncope Mayo Clinic: 1996-1998 (n=1,291) <65 years n=607  65 years n=684 13% 43% 3% 17% 24% 30% 23% 10% 18% 19% Cardiogenic Vasovagal CHS Undetermined Other

5. SYNCOPE: Natural History Kapoor: Medicine, 1990 10 20 30 40 50 60 0 1 2 3 4 5 0 1 2 3 4 5 Y ear of follow-up % Cardiogenic Undetermined Noncardiac Mortality Sudden Death

6. Emergency Department Risk Stratification of Patients With Syncope of Unknown Cause High-risk group Intermediate-risk group Low-risk group Chest pain Signs of chronic heart failure Moderate/severe valvular disease History of ventricular arrhythmias Electrocardiographic/cardiac monitor findings of ischemia Prolonged QTc (>500 ms) Trifascicular block or pauses between 2 and 3 s Persistent sinus bradycardia between 40 and 60 beats/min Atrial fibrillation and nonsustained ventricular tachycardia without symptoms Cardiac devices (pacemaker or defibrillator) with dysfunction Age =50 y With history of CAD, MI, CHF without active symptoms or signs while taking cardiac medications Bundle-branch block or Q wave without acute changes Family history of premature (<50 y), unexplained sudden death Symptoms not consistent with a reflex-mediated or vasovagal cause Cardiac devices without evidence of dysfunction Physician’s judgment that suspicion of cardiac syncope is reasonable Age <50 y With no history of Cardiovascular disease Symptoms consistent with reflex-mediated or vasovagal syncope Normal findings on cardiovascular examination Normal electrocardiographic findings

7. 85-year-old patient with valvular heart disease and congestive heart failure.

9. 51-year-old female with palpitations. Regular Rate 142 bpm No clear P waves before QRS – Not sinus rhythm Retrograde P-waves, with short RP interval

10. Mechanism of Reentry An impulse initiated in the SA node passes through both the AV node and the accessory pathway A premature atrial impulse occurs and reaches the accessory pathway when it is refractory, but conduction occurs through the AV node The impulse takes sufficient time to circulate through the AV node to allow the accessory pathway to recover initiating reentry

11. Mechanisms of Supraventricular Tachycardia AVNRT – the AV node is divided into two pathways and the activation of the atria and ventricle is synchronous so the retrograde P-wave is buried. Account for 60% of SVT. Usu are 150-200 bpm Orthodromic AVRT – mechanism seen on previous slide. Usually, L atrium is the first site retrograde atrial activation. Accounts for 30% of SVT Widened QRS Antidromic AVRT – activation occurs in the opposite direction resulting in wide complex tachycardia that is indistinguishable from V tach

15. The Thyroid and the Heart