Carotid Atherosclerosis
Anatomy
Aortic Arch
The right brachiocephalic trunk (innominate) rises from the aorta, thengives rise to the subclavian art (SCA), common carotid (CCA), & Vertebral arteries
The left aoritc arch gives direct origins of the CCA and SCA
Normal + 3 common variants
Extracranial Carotid artery
branches of the EXternal carotid artery:
Ascending pharyngeal
Superior thyroid
Lingual
Facial
Occipital
Posterior auricular
Superficial temporal
Internal maxillary
branches of the internal carotid artery before it reaches the skull:
none, no cervical branches
History of Carotid Artery and Ischemic Neurological Deficits
-old theory of "vasospasm" causing TIA's, was discredited by Pickering in the 1940's
-early 1950's Miller Fisher observed that external carotid artery atheroma was associated with ischemic CVA's
-1954 Eastcott, Pickering, and Rob successfully reconstructed a stenosed Carotid artery
-now, 80% of TIA's recognized to coincide with carotid territory
-Carotid atheromatous plaques are most frequently in the proximal (first part of the) internal carotid artery (ICA), but may include or even be exclusive to the distal CCA
Diagnostic History and Physical Exam
-carotid atherosclerosis adverse effects are exacerbated by/correlated with DM, HTN, Smoking, Male sex
Symptomatic patient
-audible bruit (swishing sounds hear with a stethascope)
-h/o amaurosis fujax (loss of vision in one eye transiently), focal neurological deficit (i.e. weakness), diagnosed central retinal artery occlusion
Asymptomatic patient
-a mid-carotid bruit (>50% stenosis)
-doppler, clinical auscultation, and MRA (angiogram done on the MRI machine) are non-invasive
-a-gram risks of TIA (transient ischemic attacks), CVA (strokes or cerebrovascualr accidents/attacks), anaphalaxis, vessel injury about 1/1000
-an arteriogram may be the only way to visualize an ulceration
-the majority of patients now undergoing surgery will need only an ultrasound and MRA, avoiding an actual arteriogram and thereby avoiding half the risks of strokes related to procedures and work ups in the past
Tests
CCT- r/o Infarct, identify remote "silent" infarcts in asx patients
MRI-earlier/more sensitive identification of infarcts
EKG, BP, ECHO, Holter-r/o cardiac source of emboli trying to diagnose dysrhythmias, etc
Natural History of Carotid Atherosclerosis
Symptomatic Carotid Stenosis
-2/3 are men with hypertension
-in the UK: 50/100,000 have TIA's/year
-200/100,000 have CVA's/year
-TIA's carry a 13 fold increased risk of CVA in the 1st year after a TIA, and a 7 fold increase/year for the next 7 years
-TIA's indicate a 10%/year risk of Sudden death (SD), CVA, or MI
-other authors quote 5 year 35% risk of CVA (Millikan)
-Heyman et al noted 5 year 23% risk of CVA with 21% of patients having MIs during those 5 years
Asymptomatic Carotid Stenosis
-only 40-50% of patients who have a CVA have an antecedent TIA
- 17-22% of "asymptomatic" patients with bruits have been noted to have silent infarcts on CCT (Berguer et al., Street et al.)
-Javid et al. followed asymptomatic patients with bruits for 1-9 years by serial arteriograms
41% had no change in atheroma
59% had a significant increase in atheroma size (variable progression rate)
Roederer et al. '84 followed 167 patients with asymptomatic bruits for 3 years (no operation)
he noted 60% had increase in atheroma size
80% stenosis carried 16% risks of CVA and 36% risks of CVA+TIA during those 3 years
Asymptomatic Carotid Stenosis risks:
1) no adverse effects
2) TIA's
3) Stroke without antecedent TIA's
4) silent occlusion
5) symptomatic occlusion
Surgical Technique
General vs Local Anesthesia
Shunt vs No- Shunt intra-operatively
-measurements of backflow
Anesthesia must maintain the BP 10-20mmHg above normal
Control BP post-operatively(extreme HTN may lead to ICH)
Surgical Pitfalls
-CN 12 damage/ansa-cervicalis
-recurrent laryngeal
-vagus
-reflex bradycardia/hypotension at the carotid body(use local anesthetic)
-allow backflow from the ICA, and occlude the ICA while the ECA and CCA are un-clamped after arteriotomy closure
Other
Carotid and Cardiovascular disease
1) mild CS + Severe CAD perform CABG
2) severe CS + stable CAD perform CEA
3) severe CS + severe CAD consider CEA and CABG at same operation
Surgical Results
- 0.5%/year risk of CVAs for patients of same age without carotid bruits serves as baseline stat
-combined surgical Morbidity and Mortality should be <5% , and is less than 1% in many experienced centers
Symptomatic
Post CEA patients carry a 1.2%/year risk of CVA
-The NASCET (North American Symptomatic Carotid Endarterectomy Trial) started in 1988 issued an emergency announcement in 2/91 that patients with symptomatic CA stenosis of ³70% linear measurement fare much better with CEA than without.
-the ECST(European Carotid Surgery Trial) started in 1981 noted a
6 fold decrease in ipsilateral CVAs vs no operation
8 fold decrease in disability/fatal CVAs
for patients with ³70% stenosis
-the also reported a 7.5% peri-operative risk of CVA (High vs the US)
-both groups continue to evaluate the benefit of CEA on 30-69% stenosis
-<30% stenosis is associated with almost no risk of CVA
The Joint Study of Extracranial Arterial Occlusion whose results were published in 1977, was a small randomized prospective study
-but the peri-operative risk of CVA/SD was an astounding 11% which negated the statistical benefits of CEA
Asymptomatic
1) Morbidity and Mortality for CEA is extremely low today in the US
2) CEA lowers the incidence of TIA's and Non-fatal strokes
3) CEA lowers the long-term stroke incidence
(cases operated and nonoperated are from the same institution)
4) CEA patients have only 1.2%/year risk of CVA vs an average of 5.27%/year risk in asymptomatic CA stenosis patients (in a recall of 7 authors' natural history series [Thompson et al.])
However, no data clearly indicates that CEA in asymptomatic or symptomatic patients changes the longevity
CEA No Operation
5 year survival 77% 66%
10 year survival 33% 39%
This reflects generalized atherosclerotic disease
Summary
Natural History
-5-12% CVA/year risk for asymptomatic patients
-almost half of patients who have CVA have no antecedent TIA
-approximately 20% of patients with "asymptomatic" bruits have CCT evidence of infarctions
Symptomatic CS
-if ³70% stenosis, operate while optimizing the patients' BP, Cardiovascular status, check EKG, etc
-heparinize if patient has recurrent TIAs
Asymptomatic CS
Currently under study
-no randomized, double-blinded, prospective study completed in the context of today's surgical M & M
-no evidence that CEA increases longevity
-definite subgroup of patients that benefits for CEA
-Await ACAS (Asymptomatic Carotid Artery Study) results for 30-69% stenosis
-may need arteriogram to evaluate for deep ulceration
-ASA, dipyridamole, coumadin?