Page 40 - Medicine and Surgery

P1: JYS
BLUK007-02 BLUK007-Kendall May 25, 2005 17:25 Char Count= 0

36 Chapter 2: Cardiovascular system

Percutaneous transluminal coronary angioplasty subsequent risk of total occlusion of the vessel. Eccentric

(PTCA) is carried out under local anaesthetic. A bal- plaques with a lipid-rich morphology are at greatest risk
loon is inflated in the coronary artery to reduce the of fissuring. Over the course of minutes, hours or days
stenosis. the plaque may fissure, thrombose over and reseal sev-
eral times, causing recurrent episodes of pain at rest or
Prognosis markedly reduced exercise tolerance. Depending on the
Prognosis is dependent on severity of disease, number of severityanddurationofocclusion,thevesselaffectedand
coronary arteries affected, left ventricular function and the presence of any collateral blood supply, this process
coexistent disease such as diabetes mellitus, peripheral may result in unstable angina, NSTEMI or myocardial
vascular disease, hypertension and renal impairment. infarction with ST elevation.

Acute coronary syndrome Clinical features
Patients present with severe ischaemic chest pain, which
Definition is identical to that of angina pectoris (central crushing
Acutecoronarysyndrome(ACS)encompassesischaemic chestpain,radiatingtojawandleftarm)butoccursatrest
cardiac chest pain of recent origin. It includes the follow- or is provoked more easily, persists for longer and often
ing: fails to respond to medical treatment. Patients require
Unstable angina describes clinical states between sta- emergency assessment and investigation to allow rapid

ble angina and acute myocardial infarction. Unstable thrombolytic therapy for those with an acute myocardial
angina is considered to be present in patients with is- infarction with ST elevation. It is essential to identify
chaemic chest pain and symptoms suggestive of ACS risk factors for and previous history of ischaemic heart
without elevation of markers of cardiac damage. It in- disease (see page 33).
cludes angina at rest lasting more than 20 minutes,
crescendo angina and angina occurring more than 24
Investigations
hours after an acute myocardial infarction.
The initial emergency investigation is a 12-lead ECG.
Non-ST elevation myocardial infarction (previously

If there is ST segment elevation or new left bundle
known as non-Q wave MI) differs primarily in that
branch block, the diagnosis is acute myocardial infarc-
the myocardial ischaemia is severe enough to cause
tion (STEMI, see page 37). If there is no ST segment ele-
myocardial damage sufficient to produce a detectable
vation,thepatientmayhaveunstableanginaorNSTEMI
rise in markers of cardiac damage (troponins and cre-
(see below).
atine kinase).
An acute, evolving or recent myocardial infarction is

defined as a rise and fall of biochemical markers of
myocardial damage (e.g. troponin or CK-MB) with at Unstable angina and non-ST elevation
least one of the following: myocardial infarction (NSTEMI)
-Ischaemic symptoms. Definition
-Development of pathologic Q waves on the ECG. Acute coronary syndrome without ST elevation (see
- ECG changes indicative of ischaemia (ST segment above).
elevation or depression).
-Following coronary artery intervention (e.g. angio-
plasty). Incidence
120,000 cases in England and Wales per annum.
Pathophysiology
As with stable angina, the underlying pathological lesion Clinical features
istheatheromatousplaque.InACSthereisfissuringofan Patients present with the acute ischaemic chest pain of
atheromatous plaque, which initiates thrombosis with a ACS.