There is a 16 segment model and a 17 segment model
16 segment model:
There are 6 basal, 6 mid and 4 apical segments
The naming is from anteroseptal and continues anticlockwise
Basal
1- Anteroseptal
2- Anterior
3- Lateral
4- Posterior
5- Inferior
6- Septal
Mid
7- Anteroseptal
8- Anterior
9- Lateral
10- Posterior
11- Inferior
12- Septal
Apical
13- Anterior
14- Lateral
15- Inferior
16- Septal
In the transgastric view one can see all the segments at a particular level.
Visualising apical segment is difficult in TOE.
Segments seen in different views:
1- Long axis view are – (130)
Anteroseptal – 1, 7 – LAD territory
Posterior – 4, 10 – LCX territory
2- 2-C view are – (90)
Anterior – 2, 8 and 13 – LAD territory
Inferior – 5, 11 and 15 – RCA territory
3- 4- C View – (10)
Lateral – 3, 9 and 14 are seen – LCX territory.
Septal – 6, 12 and 16 are seen – LAD territory
Segmental Blood supply:
1- LAD territory includes –
Septal (6, 12, 16)
Anteroseptal (1, 7)
Anterior (2, 8, 13)
2- LCX territory –
Lateral (3, 9, 14)
Posterior (4, 10)
3- RCA territory –
Inferior (5, 11, 15).
17 segment model:
Basal
1- Anterior
2- Anteroseptal
3- Inferoseptal
4- Inferior
5- Inferolateral
6- Anterolateral
Mid
7- Anterior
8- Anteroseptal
9- Inferoseptal
10- Inferior
11- Inferolateral
12- Anterolateral
Apical
13- Anterior
14- Septal
15- Inferior
16- Lateral
17- Apical
There are segments at three levels. The naming progression is clockwise.
Sunday, August 26, 2007
Imaging Artifact
Artifacts: Any structure in an ultrasound image that does not have a corresponding anatomic tissue structure.
Classification:
1. Missing structures
2. Degraded images
3. Falsely perceived images
4. Structures with misregistered location.
Missing structures:
Reasons:
Reduced resolution – To improve resolution increase the frequency, bring your area of interest into focal zone and decrease the overall gain
Acoustic shadowing – change the window.
Degraded images:
Reverberations – they are secondary reflections that occur along the path of sound pulse. They occur as a result of ultrasound bouncing between the structure and another reflecting surface. The reflecting surface may be the near side of the object, a second object or the transducer itself. The repeated journey produces two or more additional signals which are equally spaced, twice the distance as the original signal. Some times the reverberations are merged together and appear as a single solid line away from the transducer – comet tail/ring down.
Enhancements – reciprocal of image shadowing. If the intervening tissue has low acoustic impedence then the structures beyond appear to be enhanced because the sound signal is minimally attenuated. This can be adjusted by reducing the time gain compensation.
Noise – has many causes – excessive gain, cautery etc.
Falsely perceived objects:
This can be due to refraction or reverberation. Examples include:
Mirror images – Common place of occurrence is descending aorta- called as double barrel aorta. This is believed to be due to aorta-lung interface. Seen at twice the distance from the transducer as the original image.
False dissections
Line artifacts – type of reverberation artifact. Can be identified at twice the distance similar to mirror images. They mimic false intimal flaps. They can be detected as false flaps when they have indistinct borders, do not display rapid oscillatory motion and are located twice the distance from the LA wall. In addition colour Doppler does not show any interruption of flow pattern. Artifacts are more likely if the aortic diameter is >5cm and atrial-aortic ratio ≥0.6.
Reverberation artifacts are also described in the LAA mimicking thrombi. To differentiate -
Thrombus
Artifact
Confined to cavity
Not always
Has an attachment
None
Uniform consistency
Non- uniform
Texture different to LA
Similar
Twice the distance from Coumadin ridge.
Misregistered locations:
Range ambiguity – results in the display of correct structures in the wrong location. It occurs with high PRF(Pulse Repetition Frequency). This results in deeper structures appearing closer. When an unexpected object is seen in the cardiac chamber, it is due to range ambiguity.
Side lobes – are additional multiple beams emerging from the transducer in a diverging manner. Displayed as a curved line and always have a common radius from the transducer. They cross anatomical walls and cavities without regard for natural borders. They disappear with adjustment of depth/angle of the transducer.
Classification:
1. Missing structures
2. Degraded images
3. Falsely perceived images
4. Structures with misregistered location.
Missing structures:
Reasons:
Reduced resolution – To improve resolution increase the frequency, bring your area of interest into focal zone and decrease the overall gain
Acoustic shadowing – change the window.
Degraded images:
Reverberations – they are secondary reflections that occur along the path of sound pulse. They occur as a result of ultrasound bouncing between the structure and another reflecting surface. The reflecting surface may be the near side of the object, a second object or the transducer itself. The repeated journey produces two or more additional signals which are equally spaced, twice the distance as the original signal. Some times the reverberations are merged together and appear as a single solid line away from the transducer – comet tail/ring down.
Enhancements – reciprocal of image shadowing. If the intervening tissue has low acoustic impedence then the structures beyond appear to be enhanced because the sound signal is minimally attenuated. This can be adjusted by reducing the time gain compensation.
Noise – has many causes – excessive gain, cautery etc.
Falsely perceived objects:
This can be due to refraction or reverberation. Examples include:
Mirror images – Common place of occurrence is descending aorta- called as double barrel aorta. This is believed to be due to aorta-lung interface. Seen at twice the distance from the transducer as the original image.
False dissections
Line artifacts – type of reverberation artifact. Can be identified at twice the distance similar to mirror images. They mimic false intimal flaps. They can be detected as false flaps when they have indistinct borders, do not display rapid oscillatory motion and are located twice the distance from the LA wall. In addition colour Doppler does not show any interruption of flow pattern. Artifacts are more likely if the aortic diameter is >5cm and atrial-aortic ratio ≥0.6.
Reverberation artifacts are also described in the LAA mimicking thrombi. To differentiate -
Thrombus
Artifact
Confined to cavity
Not always
Has an attachment
None
Uniform consistency
Non- uniform
Texture different to LA
Similar
Twice the distance from Coumadin ridge.
Misregistered locations:
Range ambiguity – results in the display of correct structures in the wrong location. It occurs with high PRF(Pulse Repetition Frequency). This results in deeper structures appearing closer. When an unexpected object is seen in the cardiac chamber, it is due to range ambiguity.
Side lobes – are additional multiple beams emerging from the transducer in a diverging manner. Displayed as a curved line and always have a common radius from the transducer. They cross anatomical walls and cavities without regard for natural borders. They disappear with adjustment of depth/angle of the transducer.
Anatomic Pitfalls
Crista terminalis: Structure between smooth and trabeculated parts of RA. It is seen at the junction of SVC and RA. It is visualized in the bicaval view.
Eustachian valve: Valve of the IVC. It is seen in 4C / Bicaval view in 25% population at the junction of RA and IVC. It can be confused with thrombus.
Thebesian Valve: Valve of the coronary sinus. It may make coronary sinus cannulation difficult.
Chiary network: Mobile, filamentous structure seen in RA. It is probably a remnant of sinus venosus derived structures. It is associated with PFO, paradoxical embolism and interatrial septal aneurysm.
Coronary Sinus: Seen in 0 degree view as an echo free space just above tricuspid valve in the RA. If >1cm – possibility of persistent LSVC. It can also be seen in 90 degree 2-C view.
Persistent LSVC: drains into coronary sinus. It can be seen between LAA and descending aorta. It can also be seen between LAA and LUPV. In this setting it can be misinterpreted as a cyst or abscess. It should have colour flow in it. Agitated saline injection into left upper extremity vein should opacify coronary sinus and RA to confirm the diagnosis.
Trabeculations: More characteristic of RA and RV. They are caused by muscle bundles on the endocardial surface.
Pectinate Muscles: series of parallel ridges coursing along anterior surface of RA and LA.
LA is entirely smooth except for LAA.
Coumadin ridge: Junction of LAA and LUPV
Persistent LSVC drains into coronary sinus and leads to its dilatation.
Eustachian valve: Valve of the IVC. It is seen in 4C / Bicaval view in 25% population at the junction of RA and IVC. It can be confused with thrombus.
Thebesian Valve: Valve of the coronary sinus. It may make coronary sinus cannulation difficult.
Chiary network: Mobile, filamentous structure seen in RA. It is probably a remnant of sinus venosus derived structures. It is associated with PFO, paradoxical embolism and interatrial septal aneurysm.
Coronary Sinus: Seen in 0 degree view as an echo free space just above tricuspid valve in the RA. If >1cm – possibility of persistent LSVC. It can also be seen in 90 degree 2-C view.
Persistent LSVC: drains into coronary sinus. It can be seen between LAA and descending aorta. It can also be seen between LAA and LUPV. In this setting it can be misinterpreted as a cyst or abscess. It should have colour flow in it. Agitated saline injection into left upper extremity vein should opacify coronary sinus and RA to confirm the diagnosis.
Trabeculations: More characteristic of RA and RV. They are caused by muscle bundles on the endocardial surface.
Pectinate Muscles: series of parallel ridges coursing along anterior surface of RA and LA.
LA is entirely smooth except for LAA.
Coumadin ridge: Junction of LAA and LUPV
Persistent LSVC drains into coronary sinus and leads to its dilatation.
Sunday, August 19, 2007
Cardiac Intensive care
Most patients in cardiac intensive care are post surgery. The type of surgery may be CABG, valve repair/replacement, heart or lung transplant. Ocassionally patients may be admitted for preop stabilisation.
Hand Over following CABG:
1. Know the number of grafts done.
2. Whether radial artery was used.
3. Pre -op LV function. Intraop TOE finding
4. Bypass and cross clamp time
5. Intraop hemodynamic instability
6. Ease of coming off bypass
7. Post bypass supports - pharmacological, mechanical and electrical(pacing)
8. Underlying rhythm.
9. Plan
Things to do on arrival:
1. Connect to ventilator and confirm air entry and ventilator settings
2. Do 12 lead ECG
3. Monitor bleeding - inform surgeons if >400ml in first hour, >250 in next three hours.
4. See the blood gas and adjust ventilation
5. Fill in the drug chart.
6. Go through the clinical notes - co-existing illness, medications, allergies.
Hand Over following CABG:
1. Know the number of grafts done.
2. Whether radial artery was used.
3. Pre -op LV function. Intraop TOE finding
4. Bypass and cross clamp time
5. Intraop hemodynamic instability
6. Ease of coming off bypass
7. Post bypass supports - pharmacological, mechanical and electrical(pacing)
8. Underlying rhythm.
9. Plan
Things to do on arrival:
1. Connect to ventilator and confirm air entry and ventilator settings
2. Do 12 lead ECG
3. Monitor bleeding - inform surgeons if >400ml in first hour, >250 in next three hours.
4. See the blood gas and adjust ventilation
5. Fill in the drug chart.
6. Go through the clinical notes - co-existing illness, medications, allergies.
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