TRANSIENT ISCHEMIC ATTACKS OF HEART
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TRANSIENT ISCHEMIC ATTACKS OF HEART
S.Venkatesan . Madras Medical College. Chennai
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TIAs are well recognized entity in cerebrovascular circulation
“Sudden focal neurological deficit that clears completely within 24 hrs”
It’s estimated millions of episodes occur every day in elderly population
Many of them go un recognised
The only established link between TIA and heart
TIA of brain predict a ACS in the Near future
Many patients with TIA succumb to cardiac events
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Coronary vs cerebral circulation
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Both share a rich micro circulation
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TIAs
Two major forms recognized
Embolic TIA
Low flow TIA
(When cerebral auto regulation is challenged)
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Cerebral emboli sources
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The coronary circulation is the first "port of call" for blood after leaving the heart.
while cerebral blood flow must traverse many atherosclerosis prone arteries
Why TIAs are more common in cerebral circulation ?
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Low flow TIA ,lacunar & water shed Infarcts
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TIASymptoms are referred to arterial territory
Carotid,MCA,
The duration,, frequency tells us the mechanism. It can be transient motor or sensory deficits
Repetitive hand ,arm weakness indicate focal ischemic TIA
While single episode of facial weakness or transient loss of vision indicate embolic TIA
Posterior circulation TIAs
Often low flow related than embolic
Characterized by dizziness, diplopia or dysarthria
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Cerebral circulation Coronary circulation
Blood flow 750ml/mt 250ml/mt
% CO 14% 5%
O2 consumtion 19% 12%
Resistance (Cvr) 10RU 6.4RU
Collaterals developed Poor
Auto regulation Prominent Less prominent
Auto regulation Neural control Metobolism dependent
The cerebral & coronary circulation
Whats different ?
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The cerebral & coronary circulation
What’s common ?
Atherosclerosis is a diffuse disease of medium sized vessels
It does not differentiate between coronary arteries from carotid or cerebral vessels
Both have complex neural, hormonal, and metabolic control which is vulnerable under extreme physiological situations
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Vascular events in brain
TIA –RIND-Stroke in evolution – completed stroke
Vascular events in heart
Angina –Unstable angina-NSTEMI-STEMI
Clinical effects of atherosclerosis in Heart & Brain
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In the CCU it’s not uncommon to see patients with typical angina with transient ST segment shifts.
Genesis of the concept
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TIA s are called warning shots in cerebral circulation
No warning shots for heart ?
Are we not hearing it ?
or
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Aim of the study
We sought to analyse whether there could be reversible ischemic events in the coronary circulation.
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The study population
Patients who were admitted in CCU with history of transient ECG changes suggestive of ischemia with or with out angina
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14 patients
Mainly presented as Unstable angina( one following CABG)
5 Patients were referred from post operative ward (Non cardiac surgery with episodes of prolonged hypotension)
Male female ratio was 1:1.5,
Mean age 42(Range 29-68).
Retrospective –Observational study
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Typical rest angina
Atypical angina like pain during emotional stress
Post cabg anginal pains
ECG
Transient ST shifts
Runs of VPDs, NSVT
Episodes of Bradycardias
Transient AV blocks
Clinical
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Diabetes and SHT was detected in 30%.
None had previously documented CAD. (except one post CABG)
All presented with new onset ST depression >1mm at least transiently
Associated with or without angina
Cardiac enzymes were normal in all except minor elevation of CPK
Troponin not done
Clinical profile
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Echo cardiogram
(performed mean time of 30hrs(12-72h)
Global LV function was normal
2 patients showed RWMA
No other structural valve or myocardial disease were detected
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TMT
Was done in 7 patients
3 were reported positive
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coronary angiogram
Revealed normal CAG in 12.
Two patients showed non flow limiting discrete eccentric irregular lesions in proximal LAD.
Spontaneous spasm of RCA was seen in 2 patients .
Provocative tests were not done.
3 patients showed positive stress test.
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Heparin
IV NTG,
Beta blockers,
Aspirin as indicated.
All responded well with complete cessation of angina and reversal of ECG changes or both.
Management
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All patients were followed up for 6 months. Two patients developed similar recurrent ischemic events and one developed AMI.
Follow up
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Typical scenario of a patient
56y M
Post operative setting
No obvious coronary risk factors
Cardiology fitness cleared
Episodes of hypotension
ECG
Silent non specific ST dep , Runs of VPD
Settles down
Echo normal study , CAG normal , TMT normal
How do you refer to this presentation
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Chronology of Symptoms and ECG changes
Mean duration of angina was 12mts(5-60mts)
The mean duration of ST depression 20mts( 5mts-2hrs)
All patients were totally symptom free by 24h
Duration of CCU stay 6hrs-36h
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How are these clinical events to be referred?
Unstable angina?
NSTEMI?
Episodes of silent ischemia?
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Therapeutic implication
We are compelled to make a diagnosis of Unstable angina Every time there is transient ECG changes in ECG and associated with Typical or atypical angina
And in the process a patients receive a full protocol of IV anticoagulation (Heparin or LMWH)
As it’s likely many of the episodes unrelated to thrombus and are pure
Mechanical events in the coronary circulation
Economic issue pertinent
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We believe,
These ischemic episodes may be equivalent to the TIA’s of the cerebral circulation occurring in coronary micro or macro circulation
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What is the evidence for our belief ?
Currently the evidence is only sparse
Clinical recognition is largely speculative
But pathogenetic concepts cannot be proved by randomised evidence
Our study has provided a question
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Is it a transient thrombus ?
Is it a spasm?
Is it a embolus?
Is it simple coronary hypotension ?
But we are obliged to give some explanation for these events which are real
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Transient reduction in blood flow will transiently interrupt the organ function.
Heart
Has mechanical & electrical function
Brain
Has no mechanical function but rich cognitive function
Unlike brain heart cannot feel the ischemia through cognition.
It sends subtle signals one has to recognize
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Proposed mechanisms of cardiac TIA s
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Low flow TIA
&
Auto-regulation failure
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Coronary auto regulation
Pressure /flow mediated
<40mmhg with normal lumen
Neural α,β receptors. NE vasodialation
Chemical Hypoxia, H+, K, lactate,Adenosine
Mechanism of low flow TIA
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Drugs given by the anesthesiologist may affect coronary resistance
If blood pressure is low enough autoregulation fails and coronary flow becomes pressure-dependent.
This is more pronounced in patients with CAD and fixed lesion
Inadequate blood pressure compromise coronary blood flow to result in myocardial ischemia manifested in regional wall motion abnormalities, electrocardiographic changes and dysrhythmias
Drummond JC.: The lower limit of autoregulation: Time to reverse our thinking?. Anesthesiology 1997
Lessons from Anesthesia
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Embolic TIA s in heart?
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Disturbingly and unexpectedly high rate of arterial embolization in certain atherosclerotic conditions and to review the promise of newer therapeutics or devices to reduce the risk or ameliorate the sequelae of embolization
Current Perspectives
Recognition of the Importance of Embolization in Atherosclerotic Vascular Disease Eric J. Topol, MD Jay S. Yadav, MD
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Source of embolus
Platelet
Fibrin
cholesterol
Atheromatous debri
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Coronary embolism -proposed scheme
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Embolus and micro vascular obstruction
Coronary embolism - Histological documentation
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Documented by phase contrast microscopy In myocardial necrosis
Infiltration of inflammatory cellls
Fluorescence immunohistochemical staining of macrophages/monocytes
Coronary embolism Effect on myocardium
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Emboli from degenerated venous graft
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Transient ischemia and transient enzyme elevation reported after PCI, CABG
TIAs in cath lab ?
Now
Troponin levels were are elevated even following routine CAG
Percusurge and angiogaurd
Role of Distal protective devices increasing
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Conclusion
TIAs may not be an not exclusive phenomenon confining to cerebral circulation
Rarely occur in normal heart especially peri-operative setting
Many of the episodes of clinical ACS/UA could be TIA equivalents of brain
Mostly occur in the stetting of CAD, Post PCI, or CABG
These episodes likely to have different therapeutic and economic implications in the management of ACS
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“A person with the new idea is a crank until it’s proven”
Thank you