• Re-entry and Supraventricular Tachycardia
• Sinoatrial Nodal Reentry Tachycardia
• ECG and Sinoatrial Nodal Reentry Tachycardia
• Differential Diagnosis
• Carotid Sinus Massage

Re-entry and Supraventricular Tachycardia

• In supraventricular tachycardia (SVT), impulses originate in the atria or in the AV junction
• Re-entry is one of the mechanisms of tachycardia
• where the impulse circles around, most often around an anatomical barrier (scar)

• Sinoatrial Nodal Reentry Tachycardia
• Re-entry occurs in the SA node
• or re-entry passes through the SA node
• Intra-atrial Reentry Tachycardia
• Re-entry occurs somewhere in the atrium
• most often around a scar (after a myocardial infarction)
• or re-entry occurs without a barrier
• AV Nodal Reentry Tachycardia
• Re-entry occurs in the AV node
• AV Reentry Tachycardia
• It is a macro re-entry, with the impulse circling between:
• the atria and ventricles through the AV node and an accessory pathway
• There are 3 accessory pathways:
• Kent bundle (WPW syndrome)
• James bundle (LGL syndrome)
• Mahaim bundle (Mahaim syndrome)
• Atrial Flutter
• It is a macro re-entry, with the impulse circling
• through the entire, most often the right atrium

ECG and Sinoatrial Nodal Reentry Tachycardia

• Heart rate > 100/min.
• It is a narrow-complex supraventricular tachycardia (SVT)
• Width of QRS complexes < 0.12s
• P waves are of normal shape
• They are positive in lead II

Sinoatrial Nodal Reentry Tachycardia

• Heart rate > 100/min. (140/min.)
• Narrow QRS complexes (< 0.12s)
• Physiological P wave (before each QRS)
• Positive in lead II

Sinus Tachycardia

• Impulses originate in the SA node
• Each impulse creates a P wave, then proceeds to the ventricles (QRS)
• Mechanism is increased automaticity
• Sinus Tachycardia
• It is a physiological response of the body to stress, exertion, or temperature

Sinoatrial Nodal Reentrant Tachycardia

• Impulses originate in the SA node
• Each impulse creates a P wave, then proceeds to the ventricles (QRS)
• Mechanism is reentry (Impulse circles around the SA node)
• Sinoatrial Nodal Reentrant Tachycardia
• Has the same ECG appearance as sinus tachycardia
• Because impulses originate from the same location (SA node)

• Carotid Sinus Massage (CSM)
• Slows down the SA node and ectopic foci in the atria in cases of:
• Sinus tachycardia
• Atrial tachycardia
• After CSM, there was a slowing of frequency
• This indicates sinus tachycardia (The SA node has increased automaticity)
• P wave in Lead II is of normal shape

Sinoatrial Nodal Reentry Tachycardia (SANRT)

• Frequency > 100/min. (120/min.)
• Narrow QRS complexes (< 0.12s)
• Physiological P wave (before each QRS)
• Positive in lead II
• On the ECG, the pattern is sinus tachycardia
• It is almost always sinus tachycardia
• Inappropriate sinus tachycardia and SANRT are very rare
• This SVT did not respond to sinus massage (or adenosine)
• Electrophysiological study confirmed SANRT