5.5

Novacode 5.5: isolated major ST depression without Q waves or LVH — a marker of myocardial ischaemia.

Code 5.5 (Novacode NC-5.5) — isolated major ST-segment abnormality. The ECG shows significant ST depression without pathological Q waves and without left ventricular hypertrophy by the Cornell voltage criterion. Novacode classifies this pattern as isolated major ischaemia: it suggests that part of the heart muscle is not receiving enough blood, but without signs of a scar. The Minnesota equivalent is code 4-1 or 4-2.

Novacode 5ST depressionMyocardial ischaemia

Novacode criterionST-depression score ≥ 20, Q-score < 15

Exclusionno LVH (Cornell)

Minnesota equivalent4-1 or 4-2

Categorymajor ischaemia

Figure 1. Left: normal complex. Right: marked horizontal ST depression without pathological Q waves — isolated major ST abnormality (Novacode 5.5).

Why LVH is excluded

Left ventricular hypertrophy with strain produces ST depression that is not caused primarily by coronary artery disease. To keep the class specific for ischaemia, Novacode does not assign NC-5.5 when the Cornell voltage criterion for LVH is met; such ST changes are then interpreted as part of hypertrophy.

Causes

Stable coronary artery disease, silent ischaemia
Acute coronary syndrome without ST elevation
Microvascular dysfunction, severe anaemia, tachycardia
Medicines (digoxin), low potassium

Clinical significance

In epidemiological studies using Novacode, isolated major ST-T abnormalities were associated with increased cardiovascular mortality. The finding therefore warrants a thorough cardiology evaluation, even without symptoms.

Call emergency services

if you have chest pain, pressure, breathlessness, cold sweat or fainting.

Planned evaluation

Without symptoms: comparison with previous ECGs, echocardiography, a stress test or coronary imaging, and treatment of risk factors.

References

Rautaharju PM, Park LP, Chaitman BR, Rautaharju F, Zhang ZM. The Novacode criteria for classification of ECG abnormalities and their clinically significant progression and regression. J Electrocardiol. 1998;31(3):157–187.
Prineas RJ, Crow RS, Zhang ZM. The Minnesota Code Manual of Electrocardiographic Findings. 2nd ed. London: Springer; 2010. doi:10.1007/978-1-84882-778-3
Thygesen K, Alpert JS, Jaffe AS, et al. Fourth universal definition of myocardial infarction (2018). Eur Heart J. 2019;40(3):237–269. doi:10.1093/eurheartj/ehy462

This article is for general information and does not replace a consultation with a doctor. ECG findings must be interpreted by a physician together with symptoms and other tests.

Published on 14 May 2019

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