= antegrade limb thru Nl AV Nd system, w a retrograde limb via a slow concealed AP that shows decremental conduction.
Epi
-rare; <1% of SVT in kids
Sx
-usually start at <18yo; 1/2 are <1yo at start; also seen as fetus
-HR 120-250
-ECG:
-narrow QRS tachy, long RP, retro P at II/III/F, and at left lat precordial leads
-Initially HR is 200-300 as infant, then decr to 120-150 after 2yo
-bc the conduction slows thru the concealed retro AP of the circuit
-the PR interval (ie the antegrade conduction) stays near the same, only accts for 36% of the incr in cycle length
-Tends to be incessant in nature, especially in pt <2yo
-influenced by the autonomic NS & the cathecholamine state, thus there can be some variability
-& bc it can slow w age--> may delay Dx till later in life
-Can --> tachy induced CM,
-may p/w tachy/palptn, DOE< fatigue, syncope fr a decr in ventric fx; CHF Sx fr CM...
-in some pts the CM/fx may improve as tachy slows w age...
ECG
-PJRT is incessant likely bc it goes down the Nl pathway, then retrograde to a single, slow, unidirectional AP that shows decremental conduction- this all allows for the refract pd of the atria to recover (there's always an 'excitability gap')
-the conduction velocity & the refract pd of the AV Nd is faster & shorter than that of the AP
-A PVC fr RV apex or summit may--> advance, delay, or not effect the next atrial beat
-if you do see a shortening of the interval after a PVC (ie the atrial beat comes in early), then strongly consider an AP
-if you see a delay in the next atrial beat, this confirms a slow retrograde AP
-if PJRT co-exists w a pre-excitation pathway, or another concealed pathway
Tx
-resists Rx Tx often
-?amio not really effective, ?may effect AV nd rather than the AP
-if cant take to the lab, ablation is Tx of choice
EP Study
-the slow retro AP usually bridges the AV groove at R post-septal area
-1/2 are just superior to CS ostium, 3/4 are in R post-septal region in another series.
-EPS usually effective, but it is known to recur...