INOCA Flashcards
What is chronic coronary syndrome?
Coronary artery disease when recognized and intervened at an early stage, with early lifestyle changes,
pharmacological therapies and appropriate revascularization leads to favourable outcome
However, this disease is chronic, most often progressive, even in clinically apparently silent periods
Poor or late recognition of CAD, with suboptimally controlled risk factors or lifestyle modifications, increases CV
death and MI
ISCHAEMIA WITH NON-OBSTRUCTIVE CORONARY ARTERIES
Wide spectrum of symptoms and signs - often misdiagnosed as non-cardiac
Leads to under diagnosis/investigation and under-treatment
It is not a benign condition
Sequalae – recurrent angina with impaired QOL, repeated hospital admissions and invasive coronary angiograms,
increased health care cost, increased incidence of CV events
WISE (Women Ischaemia’s Syndrome Evaluation) study - 31% of all cardiovascular deaths occurred in women
without obstructive CAD
INOCA
Ischaemia with non obstructive coronary arteries
- either a coronary microvascular dysfunction (CMD) which impaired coronary physiology and myocardial blood flow in subjects with RFs causing microvascular angina and contributes to myocardial ischaemia in CAD
- or vasospastic angine in which transient vasospasm causes PZ angina and persistentvasospasm causes MI. This is present in epicardial coronary arteries.
Both these can have non-obstructive coronary atherosclerosis present
CORONARY MICROVASCULAR DYSFUNCTION
Structural remodelling of the microvasculature
→ fixed reduced microcirculatory conductance
Intimal thickening
Smooth muscle cell thickening and proliferation
Perivascular fibrosis
Capillary rarefaction
Vasomotor disorders affecting the coronary arterioles
→ dynamic arteriolar obstruction
Impaired vasodilation/increased vasoconstriction
Endothelial dependent (ACh, serotonin, histamine, bradykinine)
Endothelial independent (adenosine, catecholamines)
Diagnostic criteria for microvascular angina
Symptoms of myocardial ischamia (effort of rest angina, exertion dyspnoea), absence of obstructive CAD (invasive coronary angiography, coronary CTCA) , objective evidence of myocardial ischaemia (presence of reversible defect, abnormality or flow reserve on functional imaging) , evidence of impaired coronary microvascular function (coronary microvascular spasm, defined as reproduction of symptoms, ischeamic ECG shifts but no epicardial spasm during acetylcholine testing)
EPICARDIAL VASOSPASTIC ANGINA
Dynamic epicardial coronary obstruction due to
vasomotor disorder – muscular smooth muscle
hyperreactivity
High prevalence with smoking
Other stimuli:
Drugs
Cold exposure
Emotional stress
Hyperventilation
Allergic reactions (Kounis syndrome)
VASOSPASTIC ANGINA – COVADIS DIAGNOSTIC CRITERIA
- Nitrate-responsive angina—during spontaneous episode, with at least one of the following:
A. Rest angina—especially between night and early morning
B. Marked diurnal variation in exercise tolerance—reduced in morning
C. Hyperventilation can precipitate an episode
D. Calcium channel blockers (but not β-blockers) suppress episodes - Transient ischaemic ECG changes—during spontaneous episode, including any of the following in at least two contiguous leads:
A. ST segment elevation ≥0.1 mV
B. ST segment depression ≥0.1 mV
C. New negative YOU waves - Coronary artery spasm—defined as transient total or subtotal coronary artery occlusion (>90% constriction) with angina and ischaemic
ECG changes either spontaneously or in response to a provocative stimulus (typically acetylcholine, ergot, or hyperventilation)
Steps in diagnosing microvascular angina
Step 1) pt evaluation:
- ischeamic symptoms
- history raking inc risk factors
- physical examination
- convincing ongoing history of cardiac ischaemia
- ECG non diagnostic or normal
- cardiology referral
Step 2) Non invasive evaluation
- exercise tolerance test
- transthoracic doppler echo
- myocardial contrast echo
- myocardial perfusion imaging
- positron emission tomography
- cardiac magnetic resonance imaging
- CTCA - only preferred if low clinical likelihood, patient characteristics suggest high image quality, info on atherosclerosis desired and no CAD history
DIAGNOSIS OF INOCA – CFR AND IMR
Common non invasive ischaemia study looks at large LV regional perfusion defect
and/or wall motion abnormality
But it is ineffective for whole LV involvement like in coronary microvascular
dysfunction
No anatomical visualization of coronary microcirculation
Hence we rely on functional assessment with diagnostic guidewire +
pharmacological reactivity testing
Impaired microcirculatory conductance can be measured by coronary flow reserve
(CFR) and microcirculatory resistance is measured by indexed microvascular
resistance (IMR) – IV/IC adenosine
IMR ≥ 25 units or CFR ≤2.0 are indicative of abnormal microcirculatory function
Vasoreactivity – IC acetylcholine
DIAGNOSIS OF INOCA
– NON INVASIVE
CFR can be measured non-invasively - using endothelium-
independent vasodilators eg adenosine - with transthoracic
Doppler echocardiography [by imaging LAD flow], CMR
(myocardial perfusion index) or PET
Transthoracic Doppler echocardiography (TTDE)
Blood flow velocity measurement using PW
Locate distal LAD (apical view, predominantly diastolic signal)
Sample volume placed on the colour signal in the distal LAD
Measure peak velocity at rest and at hyperaemic state
Probe must be in the same position in both states
Non-invasive, widely available, without radiation exposure,
inexpensive; but technically challenging
PET, TTDE and MRI - IIb recommendation (i.e. may be considered) for the detection of CMD
- complex, time-consuming, limited availability and expensive
- lacks the sensitivity to differentiate epicardial vs microvascular disease with myocardial blood flow reduction
- no vasoreactivity test
Assessment of endothelium-dependent vasodilatation with IC acetylcholine
influences coronary vascular tone via muscarinic receptors on endothelial and vascular smooth muscle cells
Triggers epicardial arterial vasoconstriction (VSA) and/or microvascular spasm (MVA)
Concomitant symptoms and ECG monitoring
GTN to revert epicardial or arteriolar spasm
Low percentage of patients may develop VT/VF or bradyarrhythmias during the provocation test (3.2 and 2.7%,
respectively)
Management
Lifestyle recommendations for patients with chronic coronary syndromes
- smoking cessation
- healthy diet
- physical activity
- healthy weight
RF management
- HTN
Dyslipidaemia
- diabetes
Antianginal meds
Microvascular angina -
BB or
CCB
Nicorandil
Ivabradine
Trimetazadine
and consider statins and ACEi/ARB
Vaspospactic angine-
CCB
Long acting nitrate
Nicorandil
and consider statins and ACEi/ARB
