The Pathology of Ischaemic Heart Disease

Ischaemic Heart Disease (IHD)Definition

Refers to structural and functional abnormalities of the heart as a consequence of an inadequate blood supply

(Most cases are due to coronary atherosclerosis)

Risk Factors for IHD(Same as for Atherosclerosis)

Hypertension Hyperlipidaemia Cigarette smoking Diabetes mellitus Sedentary lifestyle Obesity Stress

Causes of IHD other than Atherosclerosis

Congenital anomalies of coronary arteries Arteritides (inflammatory conditions) Coronary embolism Coronary ostial stenosis Trauma Others – Iatrogenic injury, dissection

Clinical Syndromes of IHD

Angina pectoris Myocardial infarction Sudden cardiac death Chronic ischaemic heart disease

Pathogenesis of IHD Fixed coronary obstruction due to

atherosclerosis with significant narrowing of lumen

Secondary disruption of the plaque leading to:

Occlusive thrombosis Platelet aggregation Arterial spasm

Angina PectorisDefinition

A clinical syndrome characterized by paroxysmal chest pain resulting from transient ischaemia, which falls short of inducing infarction (cellular necrosis)

Different clinical patterns are recognized

AnginaPathophysiology

Atherosclerosis of coronary arteries almost invariably present

No specific morphological changes present in myocardium

Different clinical patterns may have correlation to pathophysiologic changes

Myocardial Infarction (MI) General

Most important form of IHD & leading cause of death in industrialized nations

Difference in race (white vs blacks) is debatable Incidence increases with age Males > females (until menopause) Predisposing factors = Those of atherogenesis

Diagnosis of Acute MI

Typical symptoms ECG changes Laboratory investigations :

Hematological - ESR, WBCBiochemical - CK, AST, LD, Troponims

(Radiographic procedures)

Pathology of Myocardial Infarction

Two major morphologic types: Transmural - involving the whole

thickness of a wall Subendocardial

Features of Transmural Infarction

Almost always occurs in the LV Extends from subendocardium to

subepicardium Thrombotic occlusion of a major coronary

vessel almost invariably present Distribution of infarction uniform: extent

variable

Relation of Coronary Artery Lesion to Location of Infarction

LAD (40-50 %) - Anterior LV

- Anterior IV septum RCA (30-40 %) - Posterior LV

- Posterior IV septum LCX (15-20 %) - Lateral wall of LV

Subendocardial Infarction Affects only inner portion of myocardium May extend beyond perfusion territory of a

single coronary artery Often multifocal Stenosis of 3 vessels often present Total occlusion of large coronary artery does

not play a significant role in the pathogenesis May be a result of marked fall in BP

Macroscopic Changes in MI<12 hr. - Not visible on gross examination

12-24 hr. - Red-blue appearance

3-4 days - Area sharply defined; border

more distinct

7-10 days - Bright yellow area

3 weeks - Thinning of myocardium - fibrous tissue becomes apparent

6-8 weeks - Scar tissue well established-white

Histology of MI Necrotic myocytes

Attract acute inflammatory response

- predominantly neutrophils (2-4 days)

- increasing macrophages (4+ days)

Granulation tissue

Fibrous tissue

Major Complications of MI

Arrhythmias Cardiogenic shock Mural thrombosis ± thromboembolism Cardiac rupture (external or internal) Ventricular aneurysm

Sudden Cardiac Death (SCD)

Death occurring within 1 hour of onset of cardiac symptoms

Other causes besides IHD exist When due to IHD, sole abnormality is

coronary atherosclerosis Mechanism of SCD attributed to a lethal

arrhythmia Term NOT synonymous with early MI

CORONARY ARTERY ATHEROSCLEROSIS

Spasm

Platelet aggregation

OCCLUSIVE THROMBOSIS

Myocardial O2 demand

Other predisposing factors

ACUTE MYOCARDIAL ISCHEMIA

ACUTE MYOCARDIAL ANGINA PECTORIS

INFARCTION

HEALED INFARCT SUDDEN CARDIAC DEATH

Current Therapeutic Modalities for Reperfusion

Intracoronary thrombolytic therapy

- Streptokinase

- Other thrombolytics Percutaneous transluminal coronary

angioplasty (PTCA) ± Coronary artery stenting

Coronary artery bypass graft (CABG)