False diagnosis of AF due to premature ventricular contractions

Tracing
N° 10
Manufacturer Biotronik Device ILR Field Biomonitor
Patient

75-year-old man participating in the LBBB-TAVI study.

Graph and trace

Episode diagnosed as AF;

  1. characteristic pattern of the tachogram suggestive of an extrasystole (premature beat followed by compensatory rest);
  2. characteristic pattern of the Lorenz plot suggestive of an extrasystole (5 different groups of points);
  3. the tracing confirms the presence of premature ventricular contractions (premature beat followed by compensatory rest) on a background of sinus rhythm; throughout the tracing, there is no fixed periodicity (bigeminism, trigeminism, quadrigeminism, etc.);
  4. diagnosis of AF with the persistence of extrasystoles.
Comments

This patient presented numerous premature ventricular contractions on a background of stable sinus rhythm triggering the automatic recording of tracings erroneously classified as atrial fibrillation. The pattern of the tachogram is characteristic with a stable baseline rhythm and presence of short intervals followed by a longer interval (compensatory rest). The pattern of Lorenz plot is also very evocative of an extrasystole with the highlighting of clearly distinct groups of points (one in the center and 4 in periphery). The variability of the ventricular intervals leads to a false diagnosis of AF which is based on the analysis of the difference between the duration of 2 consecutive sensed ventricular intervals (n, n+1). The characteristic sequence of a premature ventricular contraction (premature beat followed by a compensatory pause and then return of the baseline rhythm) if repeated over two consecutive windows leads the device to suspect the diagnosis of AF and the recording of false positives. While the interval-to-interval analysis reveals an instability in the event of an extrasystole, an analysis over several intervals conversely reveals a periodicity if the occurrence of extrasystoles is regular with bigeminism (second-order periodicity, short interval-long interval), trigeminism (third-order periodicity, normal-interval-short interval-long interval), quadrigeminism (fourth-order periodicity, normal interval-normal interval-short interval-long interval), etc.

The algorithm for the rejection of extrasystoles, in addition to interval-to-interval variability, assesses the variations in intervals on pairs of intervals in the search of a characteristic periodicity. The diagnosis of AF is only made if the device does not find a pattern compatible with a bigeminism, trigeminism or quadrigeminism. This algorithm significantly reduces the AF "load" by decreasing the number of recorded false AF episodes. Its operation however requires the presence of a regular periodicity. In this example, this periodicity is imperfect (trigeminism alternating with a quadrigeminism followed by a few intervals without extrasystole) and the algorithm is duped.