Results: 4

Figure 2

Figure 2. Measurement of mechanical PR interval from simultaneous inflow-outflow Doppler obtained from the left ventricular outflow tract. From: Overview of fetal arrhythmias.

The mechanical PR interval, indicated by parallel lines (B), is calculated from the beginning of the mitral valve ‘A’ signal to the beginning of the aortic flow signal. In this example, it measures 0.11 s with a fetal heart rate of 146 beats per minute (A).

Shardha Srinivasan, et al. Curr Opin Pediatr. ;20(5):522-531.
Figure 4

Figure 4. Algorithm for evaluation of mechanism of tachyarrhythmia based on Doppler and relationship of atrial and ventricular events. From: Overview of fetal arrhythmias.

Cases of junctional tachycardia and ventricular tachycardia with retrograde conduction may present with 1: 1 AV relationship, but there is near-simultaneous depolarization of the ventricles and atria resulting in a very short VA interval and VA<<AV. AET, atrial ectopic tachycardia; Afib, atrial fibrillation; Aflutter, atrial flutter; AV, atrioventricular interval as measured from the beginning of atrial signal to beginning of arterial flow signal; AVRT, atrioventricular reentry tachycardia; CAT, chaotic atrial tachycardia; JET: junctional ectopic tachycardia; PJRT, paroxysmal junctional reciprocating tachycardia; ST, sinus tachycardia; VA interval, ventriculoatrial time duration as measured from the beginning of arterial flow to the beginning of atrial contraction.

Shardha Srinivasan, et al. Curr Opin Pediatr. ;20(5):522-531.
Figure 3

Figure 3. Fetus with intermittent supraventricular tachycardia and preexcitation noted on magnetocardiogram. From: Overview of fetal arrhythmias.

(a) Heart rate trend (top) and actogram (bottom). Intermittent supraventricular tachycardia at rates of approximately 300 beats per minute is seen. (b) Averaged ECG showing short PR and delta wave. (c) Real-time tracing obtained from magnetocardiogram. Line 4 represents a composite of maternal and fetal signals. Maternal signals have been averaged out in 1, 2 and 3. Arrowheads point to ectopic beats with a different morphology from QRS in sinus rhythm. In line 1, the ectopic QRS is isoelectric, revealing the hidden ‘P’ (*) wave buried in the QRS, indicating ventricular or aberrantly conducted junctional ectopic beats. (d) Prenatal M-mode with premature ventricular ‘V’ beats and a regular atrial rate (A). In this scenario, the possibility of ventricular tachycardia with 1: 1 conduction becomes difficult to rule out by M-mode analysis. (e) Postnatal rhythm strip with preexcitation and ventricular ectopy.

Shardha Srinivasan, et al. Curr Opin Pediatr. ;20(5):522-531.
Figure 1

Figure 1. M-Mode and pulsed Doppler evaluation of fetal arrhythmias. From: Overview of fetal arrhythmias.

(a–c) M-mode recordings with representative SVC–Ao tracings from respective patients shown in (d–f). ‘A’ indicates atrial events and ‘V’ ventricular events. (a) M-mode recording in sinus rhythm. 1: 1 AV relationship is noted at a heart rate (HR) of 136 bpm (HR not shown). (b) M-mode recording in SVT with 1: 1 AV relation, fetal HR of 200 bpm is seen. (c) Color M-mode recording in atrial flutter with an atrial rate of 420 bpm and ventricular rate of 210 bpm indicating 2: 1 block. Here, flow in the aorta seen on color flow evaluation marked ‘V’ represents ventricular ejection. (d) SVC–Ao tracing in sinus rhythm. Parallel lines denote the mechanical PR interval, measured from beginning of atrial flow to the beginning of ventricular ejection. (e) SVC–Ao tracing in SVT. Parallel lines show the long ventriculoatrial interval of 170 ms (AV interval 130 ms). Gradual increase in HRs in tachycardia (not shown) indicated likely atrial ectopic tachycardia. (f) SVC–Ao tracing in atrial flutter showing 2: 1 block. Note: prominent ‘A’ waves. bpm, beats per minute; HR, heart rate; SVC–Ao, superior vena cava–aorta; SVT, supraventricular tachycardia.

Shardha Srinivasan, et al. Curr Opin Pediatr. ;20(5):522-531.

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