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Heart Disease (Expert Forum)
Aorta
Answered by
Cleveland - OH
This forum is for questions and support regarding heart issues such as: Angina, Angioplasty, Arrhythmia, Bypass Surgery, Cardiomyopathy, Coronary Artery Disease, Defibrillator, Heart Attack, Heart Disease, High Blood Pressure, Mitral Valve, Pacemaker, PAD, Stenosis, Stress Tests
Aorta
by Billy!, Jan 26, 2005 12:00AM
1.Do both heart mri/mra and mri/mra detect thoracic aorta aneurysms and dissections and which test does it better? 2. What's the sensivity/specifity of mri/mra in detecting thoracic aneurysms and dissections with and without iv contrast injection? 3. On internet there are several different "normal average size" measurements by mra of ascending aorta in avearge middle age men ranging from 2.5cm to 3.0cm to 3.5cm.Is ascending aorta measuring 3.5cm normal average size for normal average 50 year old man? 4. What would normal average size in cm be for aortic root,descending aorta and a ratio between ascending and descending aorta in a normal average 50 year old man?5. If for example descending aorta measures 2.0cm and ascending aorta measures 3.3cm would the difference of 1.3cm between ascending and descending aorta be normal and usually what causes such big difference? 6.Do normal average 50 year old men who were in high fitness category(endurance,marathon)most of their lives have higher ascending aorta dimensions than sedentary normal average 50 year old men and what would it be in cm? 7.If a person is having chest mri/mra for thoracic aorta are also pulmonary veins(ivc,svc) and heart imaged? 8.If inferior vena cava(ivc,svc) veins are imaged at what sizes are they considered pathology?Thanks
Doctor's Answer
by Cleveland Clinic, Jan 26, 2005 12:00AM
, Jan 26, 2005 12:00AM
billy,
thanks for the post.
whew, thats a lot of detailed questions.
1.Do both heart mri/mra and mri/mra detect thoracic aorta aneurysms and dissections and which test does it better?
The cardiac MRI is generally differs from a thorscic mri through the use of specialized software that allows the images to be coordinated to show the structures of the heart with high detail. Both scans acquire similar information but the processing differs. If you had a cardiac mri, the thoracic structures images with the mri should be seen with the same detail as a thoracic mri. The reverse is not always the case.
2. What's the sensivity/specifity of mri/mra in detecting thoracic aneurysms and dissections with and without iv contrast injection?
Generally if the scan is of high quality a dissection of the aorta can be ruled out in its entirety with very high sensitivity and specificity. MRI generally has the highest sensitivity of the imaging modalities, with similar specificity to CT and TEE. Anuerysms of the aorta are even defined even better then dissections with mri and in stable patients are the gold standard at some institutions for defining aortic pathology.
3. On internet there are several different "normal average size" measurements by mra of ascending aorta in avearge middle age men ranging from 2.5cm to 3.0cm to 3.5cm. Is ascending aorta measuring 3.5cm normal average size for normal average 50 year old man?
There are alot of factors including height, BMI and branch point variability that define how large the aorta is in a normal person. Overall these form a bell curve with most people falling under the central portion of the curve. With any variance of describing normality, even people with normal anatomy can fall at the extremes of these normal values.
4. What would normal average size in cm be for aortic root,descending aorta and a ratio between ascending and descending aorta in a normal average 50 year old man?
The mean normal value for the aortic root annulus in men is 2.6 cm and for the proximal ascending aorta 2.9 cm . The upper normal limit for the ascending aorta is 2.1 cm/m2. A value beyond 4 cm is regarded as an aneurysm, a lower value as ectasia. The normal value for the descending aorta is 1.6 cm/m2 for BSA, and aneurysm is present when a value of 3 cm is exceeded.
The aortic diameter gradually increases over time. The normal expansion rate over a period of about 10 years is between 1-2 mm and the expansion may be greater for patients with an aorta that is larger than normal.
5. If for example descending aorta measures 2.0cm and ascending aorta measures 3.3cm would the difference of 1.3cm between ascending and descending aorta be normal and usually what causes such big difference?
The descending aorta is smaller then the ascending aorta because it contains less blood after the branches from the aorta that go to the head come off. The ratio of ascending to descending aorta should normally be about 3:2 but the descending aorta can become relatively larger with age in comparison to the ascending.
6.Do normal average 50 year old men who were in high fitness category(endurance,marathon)most of their lives have higher ascending aorta dimensions than sedentary normal average 50 year old men and what would it be in cm?
no. this is not a factor in aortic size.
7.If a person is having chest mri/mra for thoracic aorta are also pulmonary veins(ivc,svc) and heart imaged?
As I mentioned, the cardiac strucures can be imaged with a thoracic mri. However, if the scan is not specifically geared towards the cardiac structres, or if the software package is not designed to image these structures then the quality may not be be seen with as high of resolution.
8.If inferior vena cava(ivc,svc) veins are imaged at what sizes are they considered pathology?
I dont have exact dimenions for normal abnormal. Some of this would depend on your overall volume status at the time of the scan as veins are very compressible and distendible. If they were dilated it would most lilely be due to congestion in the venous system from cardiac problems or shunts. Unless they were markedly dilated they probably wouldnt have really mentioned or reported them.
thanks for the post.
whew, thats a lot of detailed questions.
1.Do both heart mri/mra and mri/mra detect thoracic aorta aneurysms and dissections and which test does it better?
The cardiac MRI is generally differs from a thorscic mri through the use of specialized software that allows the images to be coordinated to show the structures of the heart with high detail. Both scans acquire similar information but the processing differs. If you had a cardiac mri, the thoracic structures images with the mri should be seen with the same detail as a thoracic mri. The reverse is not always the case.
2. What's the sensivity/specifity of mri/mra in detecting thoracic aneurysms and dissections with and without iv contrast injection?
Generally if the scan is of high quality a dissection of the aorta can be ruled out in its entirety with very high sensitivity and specificity. MRI generally has the highest sensitivity of the imaging modalities, with similar specificity to CT and TEE. Anuerysms of the aorta are even defined even better then dissections with mri and in stable patients are the gold standard at some institutions for defining aortic pathology.
3. On internet there are several different "normal average size" measurements by mra of ascending aorta in avearge middle age men ranging from 2.5cm to 3.0cm to 3.5cm. Is ascending aorta measuring 3.5cm normal average size for normal average 50 year old man?
There are alot of factors including height, BMI and branch point variability that define how large the aorta is in a normal person. Overall these form a bell curve with most people falling under the central portion of the curve. With any variance of describing normality, even people with normal anatomy can fall at the extremes of these normal values.
4. What would normal average size in cm be for aortic root,descending aorta and a ratio between ascending and descending aorta in a normal average 50 year old man?
The mean normal value for the aortic root annulus in men is 2.6 cm and for the proximal ascending aorta 2.9 cm . The upper normal limit for the ascending aorta is 2.1 cm/m2. A value beyond 4 cm is regarded as an aneurysm, a lower value as ectasia. The normal value for the descending aorta is 1.6 cm/m2 for BSA, and aneurysm is present when a value of 3 cm is exceeded.
The aortic diameter gradually increases over time. The normal expansion rate over a period of about 10 years is between 1-2 mm and the expansion may be greater for patients with an aorta that is larger than normal.
5. If for example descending aorta measures 2.0cm and ascending aorta measures 3.3cm would the difference of 1.3cm between ascending and descending aorta be normal and usually what causes such big difference?
The descending aorta is smaller then the ascending aorta because it contains less blood after the branches from the aorta that go to the head come off. The ratio of ascending to descending aorta should normally be about 3:2 but the descending aorta can become relatively larger with age in comparison to the ascending.
6.Do normal average 50 year old men who were in high fitness category(endurance,marathon)most of their lives have higher ascending aorta dimensions than sedentary normal average 50 year old men and what would it be in cm?
no. this is not a factor in aortic size.
7.If a person is having chest mri/mra for thoracic aorta are also pulmonary veins(ivc,svc) and heart imaged?
As I mentioned, the cardiac strucures can be imaged with a thoracic mri. However, if the scan is not specifically geared towards the cardiac structres, or if the software package is not designed to image these structures then the quality may not be be seen with as high of resolution.
8.If inferior vena cava(ivc,svc) veins are imaged at what sizes are they considered pathology?
I dont have exact dimenions for normal abnormal. Some of this would depend on your overall volume status at the time of the scan as veins are very compressible and distendible. If they were dilated it would most lilely be due to congestion in the venous system from cardiac problems or shunts. Unless they were markedly dilated they probably wouldnt have really mentioned or reported them.
The quote from the paper I cited says it pretty clearly - readings of 4.0 cm or greater are considered to be dilation, regardless of BSA. Other studies and doctors may put that limit higher or lower. I expect that any reading of 4.0 cm or more would require periodic monitoring (see bob_sixsix's comments, his root is at 3.8 cm and is getting regular monitoring). From comments the doctor has posted here and from discussions with two cardiologists and my surgeon, surgery is indicted when the ascending aorta and/or arch exceed 5.0 cm. I also believe that at 5.0 cm, it goes from being considered dilation to an aneurysm. You should check with your doctors as to their views on these matters.
Bob, as you say, CT is only capable of producing axial images only. MRI can produce sagittal and coronal images through the use of gradient magnets, permitting better analysis of off-axis structures such as the aorta. Newer CT systems and facilities can do 3-D reconstructions of their data, approaching the MRA in it's ability to image the aorta. CT can spot calcium deposits in the coronaries, which MRA cannot.
As far as your question on "leaflets" - the annulus is the base of the three leaflets that make up the aortic valve. I actually have a patent filed for a method of attaching a mechanical heart valve where I tested my device on pig hearts. The procedure involved excising (removing) the aortic leaflets and then introducing a cyclindrical "sizer" in this area to determine what size (diameter) mechanical valve was appropriate for the pig heart. This "sizer" would measure the diameter at the annulus where the leaflets were excised. So I would imagine that is the area being measured on the echo when it states "aortic root diameter at leaflets".
Hope that helps and good luck with your thoracic