Download Cardiac MRI PDF 440KB

Case Study | CARDIAC IMAGING
The Role of Cardiac MRI in Understanding
Physiology of Pulmonary Hypertension
in Complex CHD
By Ramiah Rajesh Kannan, MD, DNB, PDCC, Associate Professor, and
Mahesh Kappanayil, Associate Professor, Departments of Radiology
and Pediatric Cardiology, Amrita Institute of Medical Sciences
Signa* HDxt 1.5T
Cardiac magnetic resonance imaging (CMR) is emerging as a powerful,
non-invasive tool in assessment of congenital heart diseases (CHD). CMR
comprises multiple tools that combine excellent anatomical visualization, with
vital physiological information regarding blood flow and cardiac functions. It is
especially valuable in assessing young adult/teenagers as well as adult patients
with complex CHDs. Many such patients have pulmonary artery hypertension (PAH)
as sequelae. Complexities of anatomy and/or physiology in an older patient often
preclude adequate understanding through conventional imaging modalities like
echocardiography and cardiac catheterization. CMR indices to accurately predict
pulmonary artery pressures and resistances are yet to be adequately validated,
especially in association with complex CHDs. However, combination of anatomical
and physiological information obtained through CMR can aid understanding and
decision making in complex situations.
MR technique
Cardiac MRI is done using a Signa HDxt 1.5T scanner from GE Healthcare with an
8-channel cardiac array coil. All 2D FIESTA (SSFP) sequences are done in suspended
respiration in all 3 planes continuous sections across the heart in addition to
routine short axis, long axis, and outlet views.
2D FIESTA sequence
Gd-MRA sequence
2D phase contrast sequence
Minimum TR
Minimum TR and TE
20 degree flip angle
1.3 ms TE
25 degree flip angle
62.5 kHz bandwidth
60 degree flip angle
90.91 kHz bandwidth
4–6 views per segment
125 KHz bandwidth
256 X 256 matrix
128 X 128 matrix
160 x 160 matrix
2.6 mm slice thickness and ASSET
factor of 2
4 NEX
12 views per segment and 8 mm
slice thickness
MRA is done with suspended respiration using
fluoro triggering.
GEHEALTHCARE.COM/MR
44
10 mm slice thickness and
flow compensation
Fast 2D phase contrast flow studies are done
with free breathing.
SPRING 2012
Case 1:
Patient history
Case 1
An 18-year-old patient, diagnosed with complex CHD in early
Aorta
childhood presented with effort intolerance, NYHA class II;
SpO2 at 92%; single second-heart sound, continuous murmur
Aorta
over right scapular region. Patient had not undergone an
operation for CHD.
MR findings
Cine 2D FIESTA sequence showed a large conoventricular
Figure 1.
septal defect with overriding aorta (Figure 1). Post contrast
MAPCA
to left
Figure 2.
MRA showed long segment pulmonary atresia with no
native pulmonary arteries. There was a large (22 mm)
aorto-pulmonary (AP) collateral (arising at T4 level), supplying
branches to all segments of the left lung. MRA also showed
a branch from the above collateral, stenotic close to its origin
(6.5 mm), supplying the right lung with branches to all segments
MAPCA
to left
of right lung (Figure 2). MRA also showed excellent arborization
MAPCA
to right
of the right pulmonary vasculature derived from the AP
collateral and rat-tailing and poor arborization of the left
Figure 3.
Figure 4.
pulmonary arterial vasculature (Figure 3).
Phase contrast sequences were used to study the blood
flows across the aorta, the AP collateral to left and right
Clinical interpretation
lungs, the right and left pulmonary veins, and superior
and inferior vena cavae.
Patient is clinically well-preserved with SpO2 greater than
Systemic flows (Qs)
4.9 liters/minute
Total pulmonary blood flow (Qp)
9.6 liters/minute
Right pulmonary blood flow
7.6 liters/minute
Left pulmonary blood flow
2 liters/minute
Qp:Qs
Nearly 2:1
90%, with an overall Qp:Qs of nearly 2:1. Anatomically looked
amenable to total correction with ventricular septal defect
closure and right-ventricle-to pulmonary artery conduit.
However flow studies (phase contrast) clearly showed that
right lung accounts for 80% of the total pulmonary blood
flow, despite being supplied by a stenotic collateral. The left
lung, supplied by an unrestrictive, large collateral, shows
low flows (20%) with flow-pattern suggestive of high
Flow pattern in the left lung showed lower peak velocity
vascular resistance.
and rapid descent as compared to the right pulmonary
Severe pulmonary vascular disease (Eisenmengerization) of
flows (Figure 4).
the left lung with preservation of right lung resistances. CMR
flow studies clearly demonstrated unfavourable result for
total surgical correction.
GESIGNAPULSE.COM
45
SPRING 2012
Case Studies
MAPCA
to right
Case Study | CARDIAC IMAGING
Ramiah Rajesh Kannan,
MD, DNB, PDCC
is Associate Professor at Amrita Institute
of Medical Sciences.
Case 2:
Patient history
Phase contrast flow/time graphs of branch pulmonary
artery flows show rapid-deceleration pattern of elevated
pulmonary vascular resistance with left pulmonary blood
A 16-year-old patient presented with mild effort intolerance,
flow less than the right (Figure 7).
an SpO2 of 85%, and an uncertain diagnosis on previous
evaluations although truncus arteriosus was suspected.
MR findings
Cine 2D FIESTA showed a large conoventricular VSD,
two balanced ventricles, and large pulmonary artery
overriding the VSD (Figure 5). Other Cine images showed
patent ductus arteriosus shunting right-to-left and sustaining
systemic blood flow, and juxta ductal coarctation. 3D MR
SVC flows
1.3 liters/minute
IVC flows
2.1 liters/minute
Systemic flow (Qs) = SVC + IVC
3.4 liters/minute
LPA flows
2.7 liters/minute
RPA flows
3.7 liters/minute
Pulmonary flow (Qp) = RPA + LPA
6.4 liters/minute
Qp:Qs
1.9 : 1
angiography revealed aortic atresia, hypoplastic ascending
aorta, reduced arborization and peripheral pruning of
Clinical interpretation
bilateral lungs, more prominent in the left lung (Figure 6).
Based on MRI findings, the patient was correctly diagnosed
with hypoplastic ascending aorta with duct-dependent
systemic blood flow. Phase contrast flow study revealed
Qp:Qs of 1.9:1 with co-existing pulmonary vascular disease.
CMR also indicated that left pulmonary vascular resistance
is likely to be higher than the right.
Case 2
MPA
MPA
LV
Asc aorta
RV
Figure 5.
GEHEALTHCARE.COM/MR
Figure 6.
Figure 7.
46
SPRING 2012
Case 3
Coarctation
PDA
Coarctation
PDA
MPA
Figure 9.
Case 3:
Patient history
Figure 10.
Patient subsequently underwent bare-metal stenting of the
coarctation, leaving PDA open. Post-stenting CMR showed
mild increase in Qp:Qs to 1.2:1, with an increment of 34% in
A 30-year-old patient presented with features of biventricular
absolute pulmonary blood flow and moderate improvement
failure and PAH, with upper body hypertension, differential
in biventricular volumes and function.
cyanosis, and differential clubbing.
Discussion
MR findings
Cardiac MR is a useful tool in establishing morphological
Cine 2D FIESTA demonstrated a large PDA shunting
diagnosis in complex congenital heart diseases. A combination
bi-directional with a tight pre-ductal coarctation of
of CMR tools such as Cine (SSFP) images, MR angiography,
Aorta and severe biventricular systolic dysfunction.
and phase contrast (flow) studies allow unique insight into
3D MR angiography showed the complex relationship
patterns and physiology of CHD-PAH. CMR also overcomes
between the PDA and coarctation (Figures 8, 9).
the shortcomings of cardiac catheterization in accurately
Phase contrast flow/time graphs showed a pattern of PAH
assessing shunts and differential pulmonary blood flow in
in both lungs, with lower flows in the right lung and Qp:Qs
complex cardiac lesions with PAH.
of 0.9:1 (Figure 10). PDA showed a systolic right-to-left shunt
and a pan-diastolic left-to-right shunt (net flow being about
0.3L/min right-to-left).
Mahesh Kappanayil, FNB,
Pediatric Cardiology
In this case, CMR clearly showed the complex anatomy of
PDA and aortic coarctation. In addition, the Cine images and
is an Associate Professor at Amrita Institute
of Medical Sciences.
phase contrast flow study provided the detailed physiology
of circulation in the pulmonary arteries and aorta, which
was used to guide further treatment plans.
Ramiah Rajesh Kannan, MD, DNB, PDCC, is Associate Professor at Amrita Institute of Medical Sciences. He has more than five years of experience in cardiac
imaging and has performed more than 5,000 cardiac CT angiography scans (adult coronary and CHD) and more than 500 cardiac MRI exams.
Mahesh Kappanayil, FNB, is an Associate Professor at Amrita Institute of Medical Sciences. He completed his medical graduation (MBBS) from University of
Delhi in 1995, and subsequently his residency in Pediatrics. He completed his post-doctoral fellowship in Pediatric Cardiology from Amrita Institute of Medical
Sciences (AIMS), Kochi, Kerala, which is one of the leading pediatric cardiac care centers in Asia. He has continued as a faculty member at AIMS since completion
of his fellowship in 2006.
Amrita Institute of Medical Sciences in Cochin Area, India brings together a dedicated team of physicians, nurses, and other healthcare professionals to
provide the highest standards of medical treatment. The full range of primary and specialty care medical services enables cross-specialty consultation, which
assures outstanding treatment for each patient. The extensive infrastructure offers extensive facilities comprising 25 modern operating theatres, 210 equipped
intensive-care beds, a fully computerized and networked Hospital Information System, a fully digital radiology department, a 24/7 telemedicine service, and
a NABL accredited clinical laboratory.
GESIGNAPULSE.COM
47
SPRING 2012
Case Studies
Figure 8.