Coronary artery disease – need for better terminology

In the case of coronary artery disease the glut of diagnostic terms like Q-wave infarction, non-Q infarction, ST elevation infarction, non-ST elevation infarction, intermediate syndrome, unstable angina, stable angina, silent ischaemia, and exertional angina do not reflect the present day realities and are neither rational nor systematic. The term ‘acute coronary syndrome’ is too vague. A diagnostic term should be based on the cause rather than the effects. The present terms are symptom and effect based. These were relevant when there was no effective treatment. With the availability of powerful treatments these terms have become outdated. Terminology relating to the present day realities is required. In this paper I propose a system of terminology based on the assumed pathology.

Introduction

Coronary artery disease (CAD) forms the bulk of adult cardiology. Spectacular advances have been made in the diagnosis and treatment of CAD, but the diagnostic terminology has not kept pace with these developments.

The babel of terms like Q-wave infarction, non-Q infarction, ST elevation infarction, non-ST elevation infarction, etc. does not reflect the present-day realities. The term ‘acute coronary syndrome’ is too vague. A case of acute myocardial infarction successfully reperfused is no longer an ‘infarction’. There is a need to describe these cases of ‘aborted infarctions’ and ‘threatened infarctions’.¹ A properly treated case of exertional angina is no longer ‘angina’. Similarly, with sensitive enzyme markers, ischaemia, injury and infarction form a disease continuum. In the case of CAD, the current terms based on effects, were coined when proper investigations and treatments were not available. Myocardial infarction meant dead tissue and angina meant serious lifestyle limitations.

In the present era of powerful therapies, angina and infarction need not occur. When our efforts are directed at preventing these ill effects of CAD, the present diagnostic terms seem anachronistic. A better diagnostic terminology described earlier² would be appropriate.

The terminology

Basically, CAD is due to ‘obstructions’ in the coronary arteries. So the basic term used is coronary obstructive syndrome (COS). This can be of three types:

1. Total coronary obstructive syndrome (TCOS, to be pronounced “tokos”)
2. Partial coronary obstructive syndrome (PCOS, to be pronounced “pakos”)
3. Mixed coronary obstructive syndrome (MCOS, to be pronounced “mikos”).

Further, each of these can be subclassified into acute or chronic, depending on the clinical presentation. Thus, there are six terms, which were used as primary diagnoses. These are:

1. Acute TCOS or in colloquial terms abbreviated as ‘acute total’
2. Chronic TCOS or ‘chronic total’
3. Acute PCOS or ‘acute partial’
4. Chronic PCOS or ‘chronic partial’
5. Acute MCOS or ‘acute mixed’
6. Chronic MCOS or ‘chronic mixed’.

The new terms are based on the basic pathology rather than its effects. Thus, acute ST elevation infarction or equivalent, which qualifies for immediate thrombolytic or revascularisation therapy, comes under the category of acute TCOS. If treated properly, there should be no infarction. This term indicates salvageable myocardium. Infarctions past the acute stage, ischaemic cardiomyopathies and painless infarctions come under the category of chronic TCOS. These conditions do not qualify for urgent thrombolytic or revascularisation therapies. Cases in which the disease process could not be arrested can be classified as per the expert consensus document.³

Unstable angina, non-Q infarction and non-ST elevation infarction come under the category of acute PCOS. Stable angina, microvascular angina and silent ischaemia come under chronic PCOS.

A combination of the different subsets constitutes MCOS. Acute MCOS will include various combinations of the first four subclasses with at least one acute subclass. Chronic MCOS is a combination of chronic TCOS and chronic PCOS.

Usually the clinical presentation with or without electrocardiographic (ECG) evidence is the basis for the primary diagnosis. To have a complete diagnosis, the primary diagnosis was qualified by the symptom functional class, investigation results, complications, associated conditions and treatment given as and when required.

For proper documentation and research, the investigative results are ‘descriptive’ and not ‘interpretive’. Thus, an ECG is reported as “ST elevation in V1-V4” or “ST elevation in the anteroseptal leads” and not “acute anteroseptal infarction”. The same patient’s echocardiogram may be reported as “hypokinesia apical-septal segments”. The angiogram may report as “total obstruction in distal left anterior descending and 60% obstruction in circumflex”. However, an autopsy, if done, would state if there was an infarct together with its site and extent. Such a system of documentation would help in medical audit.

Mixed coronary obstructive syndromes form a unique class. As there are three major coronary arteries, different active pathologies can co-exist in each territory and in different regions of the same artery. This will include cases where the past history of CAD is known or coronary angiogram has demonstrated multi-vessel disease. MCOS is a derived concept to improve communication. The component subsets, if few and known, could be mentioned separately. Or, MCOS could be described in terms of its predominant class.

Different aetiologies can be specified in parenthesis like chronic PCOS (graft) for graft obstructions or acute PCOS (spasm) for coronary artery spasm. It is important to note that in spite of the similarities, these terms are not angiographic findings. They describe clinical situations and convey an abstract clinico-pathologic concept. Once the basic system is understood the clinician can use his ingenuity and describe any clinical situation aptly.

Use in practice

A few illustrative cases demonstrate the usage of the new terms in day-to-day practice:

1. Acute TCOS (primary diagnosis), ST elevation in V1-V4 (investigation), successful reperfusion with streptokinase (treatment). On the rounds we may say “Mr A has acute tokos with ECG changes in V1-V4”. Note: in conventional terms this is a case of acute anteroseptal infarction. This patient had no wall motion abnormalities. With our treatment at the right time, we may have prevented an infarction. It would be unfair to label this patient as ‘myocardial infarction’.
2. Chronic PCOS, exertional angina New York Heart Association (NYHA) class III, 2 mm ST depression in V4-V6 at 2 minutes Bruce Protocol, 90% obstruction in left anterior descending. Angioplasty with stent deployment done. Note: the patient no longer has exertional angina.
3. Acute MCOS, predominantly acute PCOS, Q in II, III, AVF, ST depression in V3-V6. This is a case of post-infarction angina in conventional terms.

The use of these terms will make the clinician think in terms of the actual pathology and provide a clear picture of the disease at a particular time. The concept of acute TCOS will legitimise the use of thrombolytic/intervention therapy at the earliest stage, even before ECG changes occur, and thus prevent infarctions. It can also describe a patient who had successful thrombolysis/intervention without infarction. Furthermore, it can describe ‘infarctions’ presenting with left bundle branch block and true posterior ‘infarctions’ where the current ECG-based terms (like STEMI) would be inappropriate. Asymptomatic lesions can also be described, giving scope for early treatment. Similarly, the concept of MCOS could help us optimise therapeutic strategies.

By the use of these terms, we avoid words like angina, ischaemia, and infarction in the primary diagnosis. Now these terms can at best be used as a complication of a subset of COS. The practising clinician will aim his treatment strategies at arresting these undesirable effects of coronary obstructions. This will also help in proper communication by avoiding ambiguous terms and confusing definitions.

Conflict of interest

None declared

Key messages

• Much progress has been made in the diagnosis and treatment of coronary artery diseases, however, the diagnostic terms are antiquated reflecting the era when the diagnostic and treatment modalities were inadequate
• There is a need for a new set of diagnostic terms to reflect the current realities of diagnostic and treatment progress
• Unlike other diseases, the existing terms are based on the effects or complications of the disease rather than the cause. There is a need for a cause-based terminology to improve understanding and rationalise the treatment options
• The new terms will help in planning proper treatment strategies and help in proper communication by avoiding ambiguous terms and confusing definitions

References

1. French JK, White HD. Clinical implications of the new definition of myocardial infarction. Heart 2004;90:99–106.
2. Thomas G. Classification and nomenclature for coronary artery disease (letter). Int J Cardiol 2003;88:315–16.
3. Thygesen K, Alpert JS, White HD, on behalf of the Joint ESC/ACCF/AHA/WHF Task Force for the Redefinition of Myocardial Infarction. Universal definition of myocardial infarction – expert consensus report. Circulation2007;116:2634–53.