Respective ECGs with JB, with or without a retrograde P wave, were to be agreed upon by all three cardiologists. Retrograde P wave was defined as an inverted P wave after the QRS complex was noted. Then, three cardiologists reviewed the screened ECGs and finally selected those exhibiting JB in accordance with the following: JB was defined as a regular rhythm of less than 60 beats/min without a precedent P wave and a narrow QRS complex for a duration of less than 0.12 s. The algorithm for detecting JB is as follows: no P wave, a regular RR interval (i.e., an RR interval range that is less than 10 % of the average RR interval), narrow primary beat (<0.12 s for QRS duration), and a regular rate less than 60 beats/min. Initially, the ECGs were screened by an automated ECG analysis algorithm embedded in our system to detect for JB. The low and high cut-off frequencies were 0.5 and 100 Hz, respectively.

The digital sampling rate was 500 samples per second. Twelve-lead ECGs were recorded by digital ECG instruments (General Electric Healthcare, Milwaukee, Wisconsin, USA). A total of 972,683 ECGs (mean of 2.55 ECGs per patient) stored in our electronic database system (Muse System, General Electric Healthcare, Milwaukee, Wisconsin, USA) were included in this study. We initially excluded patients who were admitted due to acute myocardial infarction or acute stroke and patients whose life expectancy is less than 6 months due to cancer. We screened consecutive patients who visited our outpatient center or were admitted to our hospital for ECG recording during the period. In the example below junctional tachycardia is seen with ('B') and without exit block ('A').We retrospectively reviewed electrocardiograms (ECGs) for 380,682 patients (47.6 ± 19.9 years male, 49.3 %) from a single university hospital from January 2008 to December 2012. Ischemia (usually from right coronary artery occlusion) and digitalis intoxicationĪre the two most common causes. There may be AV dissociation, or retrograde atrial capture may occur. The retrograde P wave may appear before,ĭuring, or after the QRS complex if before, the PR interval is usually short (i.e., 100 bpm, indicates inadequate rate control), moderate (HR = 60-100 bpm), or The PJC focus, located in the AV junction, captures the atria (retrograde) and the ventricles (antegrade). Similar to PAC's in clinical implications, but occur less frequently.(PVCs, on the other hand, are usually followed by a complete pause because the PVC does not usually perturb The pause after a PAC is usually incomplete i.e., the PAC usually enters the sinus node and resets its timing, causing the next sinus P Therefore, the fate of a PAC depends on 1) the coupling interval from the last P wave and 2) the Nonconducted PAC 'c' is now blocked in the right bundle branch and results in a RBBB QRS complex (aberrant conduction) PAC 'd' isįar enough away to conduct normally. PAC 'b' now can't get through the AV node and is Refractoriness of all the structures in the conduction system (i.e., wider boxes). In the diagram 2, seen above, the cycle length (i.e., PP interval) has increased (slower heart rate), and this results in increased

Normal conduction i.e., similar to other QRS complexes in the ECG. The resulting QRS is usually wide, and is sometimes called an Ashman beat (see PAC 'b' in diagram 1) Conducted with aberration i.e., PAC makes it into the ventricles but finds one or more of the conducting fascicles orīundle branches refractory. (see PAC labeled 'a' in the upper diagram 1) Nonconducted (blocked) i.e., no QRS complex because the PAC finds AV node still refractory. The diagram the refractory periods of the AV node and bundle branches are indicated by the width of the boxes): This is illustrated in the 'ladder' diagram where normal sinus beats (P) are followed by three possible PACs in PAC's can have three different outcomes depending on the degree of prematurity (i.e., coupling interval from previous P wave), and the The P'R interval is normal or prolonged because the AV junction is often partially refractory when the premature impulse enters it.Likes to say: 'Cherchez le P on let T' which in French means: 'Search for the P on the T wave', but it's more sexy in French!) The ectopic P wave (called P') is often hidden in the ST-T wave of the preceding beat. Occur as single or repetitive events and have unifocal or multifocal origins.Paroxysmal supraventricular tachycardia.Lesson 5 (cont) Supraventricular Arrhythmias

Junctional escape rhythm