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A few questions on the Diagnosis during Cardiac Catheterizations

I have noticed that a few patients on this site have given better explanations on heart disease then I have heard from doctors themselves. So I am going to throw a few questions out there and I hope to get some clarification.

During a Heart Cath how accurate are the percentage numbers that doctors use when they talk about blockages in arteries.
Example: During a cath if a block is said to be 40%, could it really have been 50-60% blocked and the doctors opinion was inaccurate? Is it fair to say it can be +/- 10-20% based on opinion of different doctors and different equipment used at different hospitals?
Also, regarding the Diagonal branch arteries.  Could they be identified differently by different doctors?
During a cath a doctor noted that Diag 1 had a 40% block but during a 2nd cath with a different doctor it was noted that Diag 2 had a block and not Diag 1.  
Using the example: if someone cut their cheek on their face, one doc may describe it as a cut under your eye but the other would describe it as a cut to the side of your nose.  (being the same place, just described differently)

5 Responses
976897 tn?1379167602
   When you are on the angio table, you are only seeing one side of the procedure. In another attached room (adjoining doorway and windows) there will be another cardiologist looking at your images on a computer, these are the ones they keep for records. This is where the blockages are measured and relayed back to the cardiologist doing the procedure if necessary, but these are the measurements which go onto your records and are pretty accurate.
With the example of D1 and D2 I am not sure what happened there. However, I think it's correct to say that the map of our arteries are not all the same, they form differently. The LAD and RCA are pretty much the same with us all, but some have 2xcircumflex arteries which completely go around and down the back of the heart, one from the left and one from the right. I believe this is classed as co-dominant. I would have thought many diagonals would be mapped differently in us too so it's probably just a terminology thing as you gave the example of with the cheek.
976897 tn?1379167602
Sorry, I meant to add something else.
If you have an angiogram today, which states a blockage of 40% and then a few months later you go to another hospital and have another angio, it could be stated as 50%. This doesnt mean that the first one was correct, it could obviously have grown in size.
367994 tn?1304953593
Yes, conclusions about vessel stenosis can depend on the test and the degree of blockage has different statistics is the short answer. I don't know if your are interested in the specifics but to scratch the surface the following:

There two methods to measure vessel stenosis.  There is quantitative angiography that measures the percent of the reduction of the vessel lumen (inside diameter) and a pressure-volume measurement (Functional blood flow reserve).

For some insight, coronary artery flow measurements: Coronary angiography shows the presence and degree of stenosis but not the functional significance of the lesion (ie, how much blood flows across the stenosis). Extremely thin guidewires are available with pressure sensors or Doppler flow sensors. Data from these sensors can be used to estimate blood flow, which is expressed as fractional flow reserve (FFR). FFR is the ratio of maximal flow through the stenotic area to normal maximal flow; an FFR of < 0.75 to 0.8 is considered abnormal. These flow estimates correlate well with need for intervention and long-term outcome; lesions with good FFR do not seem to benefit from stenting. These flow measurements are most useful with intermediate lesions (40 to 70% stenosis) and with multiple lesions (to identify those that are clinically most significant.

With the use of hemodynamic equations that describe the pressure loss over a stenosis, a theoretical pressure-flow relationship can be inferred that characterizes the severity of the stenosis.
Coronary arteries with a percentage area stenosis between 50% and 70% and a minimal luminal cross-sectional area between 2 and 4.5 mm2 differed significantl with respect to the coronary flow reserve, from coronary arteries with a percentage area stenosis in excess of 70% and a minimal luminal cross-sectional area less than 2 mm2.  Based on this theoretical pressure-flow relationship, coronary arteries that have a limited coronary flow reserve and critical stenosis (distal coronary perfusion pressure below 40 mm Hg at coronary flow of 3 ml/sec) can be identified with high sensitivity (83%) and specificity (82%). So in coronary artery disease the consequent reduction in coronary flow reserve can be predicted with reasonable accuracy by quantitative assessment of coronary artery dimensions.

"Fractional Flow Reserve, or FFR, is a guide wire-based procedure that can accurately measure blood pressure and flow through a specific part of the coronary artery. FFR is done through a standard diagnostic catheter at the time of a coronary angiogram (a.k.a. cardiac catheterization). The measurement of Fractional Flow Reserve has been shown useful in assessing whether or not to perform angioplasty or stenting on "intermediate" blockages".

A cardiologist must consider the point of opening up narrowings or blockages in the coronary arteries is to increase blood flow to the heart. But a number of studies have shown that if a "functional measurement", such as Fractional Flow Reserve, shows that the flow is not significantly obstructed, the blockage or lesion does not need to be revascularized (angioplasty) and the patient can be treated safely with medical therapy.      

For example, a lesion measures 50% on the coronary angiogram and the patient hasn't experienced symptoms, like angina or chest pain. Nonetheless the lesion can be seen clearly on the monitor in the cath lab (my stent implant was monitored at site of intervention not another room...reclining chair not a table). The cardiologist (and patient) may be tempted to stent the lesion (a.k.a. the stenosis) for any number of reasons. After all, there's a blockage there -- why not take care of it? This reaction has been referred to in the medical literature as the "oculo-stenotic reflex" -- you see a stenosis, so you open it up and stent it. However, a few minutes of measurement with a special guide wire may reveal that an intervention won't have a significant impact on this particular blockage. Being able to better select cases not only saves health care costs, but contributes to more appropriate patient care.

A statistic:The special guide wire crosses the lesion and is able to measure the flow and pressure of the blood. Results are displayed on a special monitor (left) along with the "FFR value". Studies have shown that an FFR value less than 0.75 or 0.80 corresponds to inducible ischemia, and most likely will require interventional treatment. Blockages that score above this threshold can be safely and adequately treated by medical therapy without the need for angioplasty.

But to read the pressures, the balloon needed an extra lumen, which made the balloon too large to get through very tight lesions or into smaller arteries. Lower profile balloons were invented, but they could not measure pressures, so this concept of measuring pressures virtually disappeared, to the chagrin of a number of cardiologists
The purpose of this study was to investigate differences between prestenotic and poststenotic intracoronary Doppler flow velocities and to determine whether these hemodynamic parameters of coronary flow demonstrate a correlation with geometrically measured coronary artery stenosis.

A low-profile (0.018-in.) Doppler angioplasty guidewire capable of providing spectral flow velocity data was used to measure blood flow velocities both proximal and distal of 95 coronary artery stenoses ranging from 15% to 82% in diameter. Percent diameter stenoses were analyzed by quantitative coronary arteriography.

In comparison with prestenotic measurements poststenotic Doppler flow velocities were markedly reduced in coronary artery stenoses with a diameter reduction greater than 50% in quantitative angiography. In stenoses less than 50% no difference between prestenotic and poststenotic parameters of coronary flow could be found. Prestenotic Doppler data demonstrated no correlation to percent diameter stenosis, whereas poststenotic flow data correlated moderately with percent diameter stenosis. Poststenotic Doppler data of stenoses below 50% differed significantly from stenoses above 50%.

In conclusion, intracoronary Doppler flow velocity measurements performed distal to coronary artery stenoses contribute to the evaluation of hemodynamic significances of particular coronary artery stenoses using quantitative coronary angiography, coronary flow reserve from digitized coronary angiograms, quantitative left ventricular angiography
The calculated pressure drop was highly predictive of the thallium scintigraphic results with a sensitivity of 94% and a specificity of 90%. The calculated pressure drop is a better anatomic variable for assessing the functional importance of a stenosis than is percent diameter stenosis or obstruction area. However, the 95% confidence limits of the relation between pressure drop and coronary flow reserve are wide, making the measurement of coronary flow reserve an indispensable addition to quantitative angiography, especially when determining the functional importance of moderately severe coronary artery lesions.
976897 tn?1379167602
Interesting, so if doppler technology exists for coronary arteries, then why can't they work out using this technology if someone has microvascular disease?
There are only two entry points for blood to heart tissue, the left main stem and the right coronary artery. Surely, at a given heart rate, we must be able to calculate what a normal flow would be throught those two vessels. If the flow rate is significantly less, and no blockages are seen in the major coronary arteries, surely we can assume microvascular disease? Basically blood can only enter in two places and this blood all has to end up going through capillaries, giving a continual flow.
If I had two garden hoses feeding a large irrigation system in my garden, consisting of millions of tubes with tiny holes, I could tell if a high proportion were blocked by a reduced flow in the two hose pipes.
367994 tn?1304953593
QUOTE: "There are only two entry points for blood to heart tissue, the left main stem and the right coronary artery. Surely, at a given heart rate, we must be able to calculate what a normal flow would be throught those two vessels. If the flow rate is significantly less, and no blockages are seen in the major coronary arteries, surely we can assume microvascular disease? Basically blood can only enter in two places and this blood all has to end up going through capillaries, giving a continual flow".

Flow is not the definitive variable in an expression for anything other than the inter-relationship with gradient pressure and resistence.....For review:  In the body, the relationship clearly shows the dominant influence of vessel radius on resistance and flow and therefore serves as an important concept to understand how physiological (e.g., vascular tone) and pathological (e.g., vascular stenosis) changes in vessel radius affect pressure and flow, and how changes in heart valve orifice size (e.g., in valvular stenosis) affect flow and pressure gradients across heart valves. I believe we have a discussion on that subject, and we went through the mathematical formula.  The inter-relationship CHANGES within segments of the entire configuration.  Example the segment between or across a gradient and around a tortuous segment, etc.will have higher pressure.

>>>The etiology for microvascular disease is different than coronary artery disease. Plaque narrows the coronary arteries and reduces the flow of oxygen-rich blood to the heart muscle. As a result, the heart doesn't get the oxygen it needs. This is known as ischemic heart disease.

In coronary micro vessel disease ( MVD), plaque can scatter, spread out evenly, or build up into blockages in the tiny coronary arteries. In coronary MVD, however, the heart's smallest arteries are affected. Plaque doesn't always create blockages as it does in coronary heart disease (CHD). For this reason, coronary MVD also is called nonobstructive CHD.

I like to think of MVD as nonobstructive coronary artery disease and may be diagnosed when a patient complains of chest pain but, unlike in typical obstructive coronary disease, shows little or no evidence of plaque blocking the arteries.

Nonobstructive CAD was once thought to be a benign condition, and patients were released with a diagnosis of nonspecific chest pain.  It is now known that having nonobstructive CAD puts patients at higher risk of developing future heart conditions. Even with no blockage in the arteries, patients with nonobstructive CAD and angina pain are at risk of recurring coronary events such as myocardial infarction (heart attack) and death from heart attack.

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