Case 2

Stem: 77 year old woman had back pain yesterday, and several episodes of feeling faint today. She has not experienced any anterior chest discomfort. On arrival her blood pressure was 110/80 mm Hg, her JVP was 0.5 cm, and there was no leg oedema. Examination of the lungs and heart and abdomen was normal.

+ List the significant findings in the ECG and provide the most likely or important diagnosis

  • The rhythm is regular, and the ventricular rate is about 26 beats per minute
  • The QRS complexes have a right bundle branch block morphology and left axis deviation is present i.e a bifasicular block is present (1)
  • Each QRS complex is preceded by three P waves, only one of which is conducted. The PR interval of the conducted P waves is constant (at 0.20 seconds). The atrial rate is about 80 beats per minute. The underlying rhythm is sinus rhythm with 3:1 AV block; this is termed advanced 3:1 AV block rather than Type II second degree heart block
  • The QT interval is prolonged at 600 msec (2)
  • Horizontal ST depression is present in Leads I, II, V4 to V6; sagging ST depression is seen in Lead V3 (3)
  • Relevant normal observations: The transition zone is between V2 and V3

Notes:

  1. The PR interval of the conducted P waves is at the upper limit of normal; if it was longer than the 0.20 seconds seen in this case the term trifasicular block would be used.
  2. Measurement of the QT interval is complicated because P waves merge into the end of each T wave. The QT interval is prolonged in both congenital heart block and acquired heart block; this prolongation can lead to the development of torsade de pointes. The QTc in this case (using the Framingham formula for QTc [QTc = QT + 0.154(1-RR) where RR = 60/HR]) is still prolonged at 598 msec.
  3. These changes raise the possibility of ischaemia
  4. The patient received an intravenous infusion of isoprenaline to increase the ventricular rate to 50 beats per minute, and had a permanent pacemaker inserted the next day.