Q. What is Atrial Extrasystoles?
Atrial premature beats often occur at lower workloads and have little significance. As exercise increases, they usually subside and may then return during recovery. Supraventricular extrasystoles however, may be an aid in the identification of ischaemia. When the atrial extrasystolic beat has ST depression greater than the preceding sinus beat, it has been shown to be a marker for ischaemia. Michaelides and associates34 reported a sensitivity of 74 per cent and a specificity of 84 per cent for this little recognized finding. It has also been reported that the R-wave in supraventricular beats in ischaemic patients is taller than that in the normally, conducted beats. In normals, the premature "R"-wave is shorter than in the previous beat. An increased R-wave or no change in premature supraventricular beats has a sensitivity of 79 per cent and a specificity of 90 per cent in those who had exercise induced premature supraventricular contractions. When some baseline ST depression is present and the premature atrial contraction shows less deviation than the sinus beat, then ischaemia is rare. When a nodal premature beat is followed by a long pause and the following sinus beat shows accentuated ST depression, ischaemia is also likely.