"Patrick Blanchard, M.D." wrote:
> On Thu, 04 Dec 2003 17:38:06 GMT, Dr. Andrew B. Chung, MD/PhD
> <andrew@heartmdphd.com> wrote:
>
> > "Patrick Blanchard, M.D." wrote:
> >
> >> On Thu, 04 Dec 2003 04:20:56 GMT, Dr. Andrew B. Chung, MD/PhD
> >> <andrew@heartmdphd.com> wrote:
> >>
> >> > smf114@mindspring.com wrote:
> >> >
> >> >> I just a mibi done. I'm in my early 40's, get only the minority of
> >> >> chest pain which sometimes I wonder if it's GI related. It's
> >> fleeting
> >> >> and usually very specific to what I would say is my PMI area. I also
> >> >> have mildly elevated chol and have normal BP. I used to smoke but
> >> >> quit 15 years ago. There is cardiac history in my family but only in
> >> >> the 70's.
> >> >>
> >> >> My Mibi shows an "area of concern." My doctor sent me at my request
> >> >> because I wanted a stress test before I start exercising again since
> >> >> it's been a few years.
> >> >>
> >> >> My main question is, how accurate are these?
> >> >
> >> > Specificity is around 85-90%.
> >>
> >> And this is for coronary flow obstruction only, which is a late
> >> manifestation of atherosclerosis.
> >
> > Patrick,
> >
> > Aren't you confusing sensitivity with specificity here?
>
> Assuming that coronary flow obstruction is causing myocardial ischemia
> which in turn is causing smf114@mindspring.com's chest pain, no.
>
> >
> > When we talk about sensitivity, we are describing a test's ability to
> > detect
> > something.
>
> A very high sensitivity, when negative, rules out disease. The disease a
> MIBI nuclear perfusion scan rules out is myocardial ischemia from any
> cause.
>
Correct. The most common cause of inducible ischemia (typically 99%) is
occlusive coronary atherosclerosis.
>
> > Here you would be correct that the "mibi" only detects ischemia or
> > infarcted myocardium. This would indicate advanced atherosclerosis.
>
> yes, but again, we both are assuming the myocardial ischemia is from
> atherosclerosis.
>
If not occlusive atherosclerosis, then endothelial dysfunction which is highly
associated with non-occlusive atherosclerosis.
>
> > However,
> > imho, the late manifestation of atherosclerosis is death and not
> > ischemia.
>
> we must agree to disagree here, as we have many times before about the
> definition of atherosclerosis.
>
Here we seem to be disagreeing on the definition of "late."
>
> >
> > Otoh, when we talk about specificity, we are describing what it means
> > when a
> > test is positive (i.e. the likelihood it is a true positive result).
>
> Yes, you are correct about specificity. It has everything to do with
> ischemia but not necessarily occlusive atherosclerosis.
The latter would be factored into lowering the specificity. As you should be
well aware, the gold standard for determining both sensitivity and specificity
is the cardiac cath (ie coronary angiography).
> A very specific
> test, when positive, rules in disease. For a MIBI nuclear perfusion scan
> the test is for myocardial ischemia. Most often myocardial ischemia is
> caused by flow limiting atherosclerosis and not, say, trauma.
It is not clear to me why you brought up trauma. Nonetheless, a defect on a
"mibi" could mean either ischemia or myocardial scar. The scar would be from
past infarction.
>
>
> > This has
> > nothing to do with the tests ability to detect non-occlusive (less
> > advanced)
> > atherosclerosis.
>
> yes, a MIBI scan is not used to detect non-occlusive disease.
>
> >
> >> MIBI scans cannot detect non-intrusive
> >> atherosclerosis
> >
> > You probably mean non-occlusive.
>
> No, I mean non-intrusive,
I have never seen this terminology you are using. Is this term "non-intrusive
atherosclerosis" your invention?
> assuming that there is no plaque vulnerability
> upstream of ischemic myocardium.
Is this ever the case?
There is such as a thing as decreased plaque vulnerability but is there really
such a thing a *no* plaque vulnerability? Or is this another invention of
your?
> Non-intrusive atherosclerosis will not
> result in occlusion unless vulnerable plaque triggers thromboembolic
> episodes.
Reading between the lines, are you defining non-intrusive atherosclerosis to
mean atherosclerosis that has no chance of rupturing (ie plaques but
*invulnerable* ones)?
> For silent non-intrusive atherosclerosis, a MIBI nuclear scan
> will be negative;
Not if there is flow-limiting occlusion (ie occlusive coronary disease).
> MIBI scans cannot detect (silent) non-intrusive
> atherosclerosis.
>
Are you confusing silent ischemia with non-occlusive coronary disease?
>
> Non-intrusive is found with positive remodeling of the artery; an atheroma
> is present, can be vulnerable, but does not intrude into the arterial
> lumen. Non-intrusive positive remodeling continues for quite some time in
> non-diabetics.
>
> http://tinyurl.com/xs30
>
Your reference is about the carotid as an indirect way of assessing what may be
going on in the coronary arteries during the ACS. The authors don't define
your term "non-intrusive atherosclerosis."
>
> The carotid IMT of 75 patients with multiple complex coronary plaques was
> significantly larger than that of 50 patients with solitary plaques (p <
> 0.0003). CONCLUSIONS: In acute coronary syndrome, multiple complex coronary
> plaques are associated with positive carotid remodeling, suggesting that
> plaque vulnerability may be a systemic phenomenon.
>
> http://tinyurl.com/xs40
>
> RESULTS: Soft plaque was observed more frequently in acute than in stable
> coronary syndrome (59% vs 31%), whereas hard plaque was more common in
> stable coronary syndrome (69% vs 41%) (P = 0.03). The EEM CSA (15.11 +/-
> 2.89 mm(2) vs 13.25 +/-3.10 mm(2), P = 0.019) and plaque CSA (10.83 +/-2.62
> mm(2) vs 9.30 +/-2.84 mm(2), P = 0.035) were significantly greater at
> target lesions in patients with acute rather than stable coronary syndrome,
> while lumen CSA and percent area stenosis were similar in both groups. RI
> was significantly higher (1.08 +/-0.16 vs 0.95 +/-0.14, P = 0.002) and
> positive remodeling was more frequent in acute coronary syndrome (53% vs
> 23%, P = 0.019), whereas negative remodeling was more common in stable
> coronary syndrome (58% vs 24%, P = 0.007).
>
Still don't see where you get the terminology you are using.
>
> >
> >> which is often the cause of an acute coronary syndrome.
> >
> > During ACS, the disease is no longer non-occlusive.
>
> ahem...
> http://tinyurl.com/xs40
>
> RESULTS: Soft plaque was observed more frequently in acute than in stable
> coronary syndrome (59% vs 31%), whereas hard plaque was more common in
> stable coronary syndrome (69% vs 41%) (P = 0.03).
>
> The mechanism of occlusion in acute coronary syndrome results from
> thromboembolism, not from the actual atherosclerosis.
Nonetheless, we call this occlusive coronary disease at this point.
> Thrombosis, although
> associated with atherosclerosis, is a triggered event of platelet
> aggregation. Occlusion can occur without thrombosis, albeit much slower,
> but can occur exclusively from atheroma growth without thrombosis and with
> an intact fibrous cap. In other words, someone can have a non-occlusive
> vulnerable atheroma giving rise to acute coronary syndrome. In fact, non-
> occlusive atheromas, or vulnerable plaques, are the primary cause of ACS.
>
> >
> >> I
> >> would encourage you to find out more specifically what "area of concern"
> >> really means by asking your doctor for more information, or send your
> >> report to me and I'll give you my 2 cents worth.
> >>
> >
> > Or the report can be described and discussed here for more than 2 cents
> > of
> > information.
> >
> >>
> >> >
> >> >> I really don't want to
> >> >> have a cath which I assume is the next step.
> >> >>
> >>
> >> you are correct, and unfortunately it is often the next step regardless
> >> of
> >> the outcome of the nuclear scan.
> >>
> >
> > Why is this unfortunate, Patrick?
> >
> > And why would a normal mibi scan lead to a heart catherization in your
> > community? (it doesn't in mine)
>
> Often is the key word. Not always, but often.
>
> In this study, 15% of the time.
>
> http://tinyurl.com/xred
>
> The study population consisted of 334 patients. Their mean age was 56 +/-10
> years, and 80% were men. Of the patients, 30% were asymptomatic, 29% had
> angina, and only 6% had recent acute myocardial infarction or unstable
> angina. Fifty-one patients (fifteen percent) were subsequently referred for
> coronary angiography.
>
Ok, 15% had a "positive" myocardial imaging result in this Lebanese cardiac
center. This is hardly surprising since 6% had a heart attack and 29% had
angina.
>
> I would consider 15% "often" considering the risk of coronary angiography
> and its kissing cousin, angioplasty. http://tinyurl.com/xrwg
>
Your reference does not say 15% of "normal" myocardial perfusion imaging
results lead to heart catheterizations, now does it?
>
> The author of the original post, smf114@mindspring.com, was told "an area
> of concern" was identified on his MIBI scan. This is really a euphemism for
> "let's warm up the cath lab".
Does it really? <raised eyebrow>
>
>
> >> >
> >> > Then discuss your concerns with your cardiologist. S/he should go
> >> over
> >> > the decision tree with you. Ultimately, it is your decision whether
> >> to
> >> > have the procedure.
> >> >
> >>
> >> As to risk of the procedure, seek them out.
> >
> > These should be enumerated on the informed consent form that one signs
> > giving
> > the cardiologist permission to perform the procedure. One can ask to
> > review
> > this form a few days or more before the procedure, if one wish.
> >
> >> You might be suprised.
> >
> > Why would I be surprised by the risks?
> >
> > You probably are referring to the original poster (Why aren't you
> > responding to
> > that post instead?)
>
> Yes, I should have posted this elsewhere; it was not directed at you.
>
> >
> >> MIBI
> >> scans require an intravenous dose of radioactive dye.
> >
> > Correct.
> >
> >> There is no safe dose
> >> of radiation, no matter how low the exposure.
> >>
> >
> > Depends on your definition of "safe"
>
> There is no safe dose.
>
As you are reading this, you are getting a dose of radiation. If you truly
believed that no amount of radiation is safe, why are you using your computer?
>
> >
> >>
> >> A heart cath carries even more risk for complications.
> >
> > It does.
> >
> >> I remember quite
> >> well a patient of mine, 45 years of age, with chest discomfort,
> >> underwent
> >> the course of evaluation you are pursuing now.
> >
> > You probably are trying to respond to the original poster.
>
> yes.
>
> >
> >> I met her while serving as
> >> the attending resident on the stroke rehab unit. She is now in a nursing
> >> home and cannot converse with her children. Her heart, however, was just
> >> fine.
> >>
> >
> > Strokes should be listed as a possible complication of a heart cath
> > albeit a
> > rare one.
>
> http://tinyurl.com/xrxy
>
> ...and quite tragic.
>
Your reference describes the overall complication rate as being very low.
Humbly,
Andrew
--
Dr. Andrew B. Chung, MD/PhD
Board-Certified Cardiologist
http://www.heartmdphd.com
