ST-segment elevation

N° 24
23-year-old man hospitalized for syncope with history of familial sudden death;
57-year-old man with multiple factors hospitalized for typical chest pain;
ST-segment elevation

Except for the early repolarization pattern, the normality criterion for ST segment elevation is that the ST segment must not deviate more than 1 mm above the isoelectric line. This electrocardiographic sign taken individually is poorly specific; to facilitate diagnosis, it is essential to know the clinical context (thoracic pain, neurological disease, etc), to specify the characteristics of the elevation (amplitude, concave or convex, localized or diffuse, territory and leads involved, etc) and to look for associated electrical signs (conduction disorder, necrosis q wave, SIQ3 pattern, left ventricular hypertrophy, QT-interval, etc). It may also be important to repeat the recording of the tracing to establish its stable or evolving nature. Various diseases and clinical situations can be associated with a ST segment elevation:

  • myocardial infarction: this is the first etiology to exclude, especially in the context of chest pain; the characteristic pattern is that of a Pardee wave with an elevation that is preferentially convex upwards, broad, corresponding to a defined coronary territory, ending with a negative T-wave and, depending on the reperfusion time, appearance of a necrosis q wave; a reciprocal depression is frequently observed in the opposite leads; the pattern evolves over time with reversal of the polarity of the T-wave and return of the ST segment to the isoelectric line; the remote persistence of a significant elevation associated with a necrosis q wave should evoke the diagnosis of aneurysm of the left ventricular wall;
  • Prinzmetal's angina: the most characteristic electrocardiographic sign of coronary vasospasm is the presence of a ST segment elevation, occurring during chest pain, often very ample (> 10 to 15 mm in extreme forms), convex upwards, beginning at the peak of the R wave, encompassing the T-wave and constituting a prolonged monophasic coved wave of 320 to 360 ms; the elevation topography is dependent on the coronary artery presenting the spasm; there may also be indirect images of deep reciprocal ST segment depression in the opposite leads;
  • acute perimyocarditis: ST segment elevation is relatively characteristic since widespread, most often maximal in leads I, II and from V4 to V6 with possible reciprocal depression in aVR and V1; this depression is transient, generally small (≤ 5 mm), ascending and concave upwards in its initial portion;
  • left bundle branch block: there is generally an appropriate discordance between the ST segment and the T-wave in precordial leads (elevation and positive T-wave if negative QRS, depression and negative T-wave if positive QRS); an elevation in the right precordial leads (V1, V2) is therefore frequent; failure to observe the appropriate discordance should evoke the presence of a myocardial infarction in the setting of typical chest pain;
  • left ventricular hypertrophy: it is also common to find an appropriate discordance with elevation in the right precordial leads;
  • right ventricular pacing: in right ventricle-paced patients, the electrical pattern can be similar to that observed for a left bundle branch block with possible evidence of elevation in the right precordial leads;
  • Brugada syndrome: this is a familial channelopathy with risk of sudden death; the diagnosis is made from the electrocardiogram with the detection, of a typical coved ST elevation pattern V1, V2, V3;
  • others: hyperkalemia, increased intracranial pressure, cardiac tumor, myocarditis, pulmonary embolism, etc.
In the presence of chest pain and a ST segment elevation, certain signs are suggestive of an ischemic origin: convex upward elevation, broad, corresponding to a defined coronary territory, with negative T-wave and necrosis q wave, evolving over a period of a few hours.