In this chapter, we address the basic notions of the differential diagnosis of
cardiac ischemia. Hypertrophic obstructive cardiomyopathy or HOCM is characterized
on the electrocardiogram by Q waves in the inferior leads and negative T waves from
V2 to V5 which is difficult to distinguish from classical ischemia due to coronary
pathology.The electrocardiographic abnormalities of pericarditis are non specific and
sometimes difficult to distinguish from ischemia. They are typically recognized by PR
segment depression, present in the majority of the leads. The repolarisation
abnormalities it causes are very similar to those of ischemia-lesion; primarily, the ST
segment is elevated, with an inferior convexity, the so-called “camel hump” appearance.
This segment progressively returns to the isoelectric line in the same time it takes for
the amplitude of the T wave to fall, and in the end becomes negative. In V5, the
amplitude of the ST elevation, compared to the amplitude of the T wave is > 0.25: a
ratio < 0.25 favours early repolarisation. The electrical features of pericarditis are
reputed to be diffuse, but in reality are not always so. Occasionally, acute pericarditis is
the cause of an arrhythmia, almost always supraventricular (atrial fibrillation).
However, there is never a pathological Q wave of necrosis. Moreover, the changes are
generally diffuse and widespread without systemization of coronary abnormalities. The
electrocardiographic features of pulmonary embolism are not specific: on the
background of preexisting right bundle branch block, the Q waves in III and QS in V1
could be due to an inferior or an antero-septal infarct respectively. In the same vein, the
raised ST segment in V1 could also be an antero-septal ischemia-lesion picture.
Chatterjee phenomenon is a T wave inversion, often deep, which occurs after a period
of abnormal ventricular activation (broad QRS), notably ventricular tachycardia,
intermittent left bundle branch block or preexcitation, or even intermittent ventricular
pacing. Early repolarisation causes in leads V2 to V5, a raised J-point and ST segment,
as well as an increase in the amplitude of a symmetrical T wave, as would be expected
for an ischemia-lesion but the J-point remains prominent and the convexity of the ST is
inferior and not superior. Brugada syndrome is not a conduction abnormality but
deserves a mention under the heading of right bundle branch block as it can mimic some
aspects, notably changes in the terminal phase. There are 3 types of changes in V1 and
V2 and rarely in V3. In all 3 types the J-point is raised at least 2 mm.
Keywords: Pericarditis, hypertrophic cardiomyopathy, Chatterjee phenomenon,
early repolarization, Brugada syndrome, PR segment depression, ST segment
elevation, pulmonary embolism, rigth ventricular dilatation.
