Case Author(s): Lisa Oakley, M.D. and Robert Gropler, M.D. , 12/31/97 . Rating: #D3, #Q3

Diagnosis: Right Heart Failure Secondary to Primary Pulmonary Hypertension

Brief history:

50 year old woman with progressive shortness of breath.

Images:

CARDIAC BLOOD POOL STUDY

End diastole (top), End systole (bottom)

View main image(ca) in a separate image viewer

Full history/Diagnosis is available below

Diagnosis: Right Heart Failure Secondary to Primary Pulmonary Hypertension

Full history:

50 year old woman with a history of primary pulmonary hypertension, being evaluated for possible lung transplant.

Radiopharmaceutical:

Tc99m in vivo labeled red cells

Findings:

The most striking abnormality is marked right heart enlargement. The main pulmonary artery is significantly dilated. The right atrium is moderately dilated, but contracts normally. The right ventricle is markedly dilated and is diffusely hypocontractile. The calculated equilibrium phase right ventricular ejection fraction is 18%.

The LV/RV stroke count ratio is decreased (0.31), suggestive of tricuspid regurgitation.

The left atrium and ventricle are normal in size and configuration. Both chambers contract normally and the calculated left ventricular ejection fraction is 55%.

Discussion:

The most accurate method for determining the right ventricular ejection fraction (RVEF) is by first-pass radiolnuclide ventriculography, which allows for complete separation of the right atrium and ventricle. An approximate estimation of RVEF may be obtained (as in this case) by equilibrium radionuclide ventriculography. This method is often limited by overlap of the right atrium with the right ventricle during diastole leading to a falsely decreased value. The lower limit of normal for the right ventricular ejection fraction is 40-45%.

The calculation of ejection fraction is (ED - ES) / (ED - background) X 100.

Right ventricular ejection fraction is particularly dependent on the afterload faced by the right ventricle. Decreased RVEF often reflects increased pulmonary artery systolic pressure or increased pulmonary vascular resistance.

The stroke count ratio (SCR) was developed to assess for the presence of valvular regurgitation. This calculation relies on the assumption that in the absence of any right sided regurgitation or intracardiac shunts, the left ventricular (LV) and right ventricular (RV) stroke volumes should be equal. In cardiac blood pool imaging, stroke counts can be substituted for stroke volumes because the two are proportional. Therefore, the change in counts between diastole and systole of the left ventricle divided by the same change in the right ventricle should equal one in the normal patient.

With left sided valvular regurgitation, the SCR is elevated (LV stroke volume increased) and with right sided regurgitation, the SCR is decreased (RV stroke count increased). This value is only valid in isolated valvular lesions because balanced bilateral lesions (ie. similar degrees of tricuspid and mitral regurgitation) may in fact cancel each other out. Also, if there are two ipsilateral valvular lesions (ie. concomittant aortic and mitral regurgitation) the ratio will reflect the sum of the lesions.

Followup:

The patient subsequently underwent bilateral lung transplant with a repeat cardiac blood pool study (follow up image).

The results are dramatic! In essence, the cardiac function is now normal with complete recovery of the right ventricular function. In fact, the right atrium and ventricle are normal in size and the RVEF is now 45%.

View followup image(ca). CARDIAC BLOOD POOL STUDY (POST LUNG TRANSPLANT)

End diastole (top), End systole (bottom)

Major teaching point(s):

This case demonstrates the right ventricle's ability to completely restore function when the afterload is reduced. In other words, when pulmonary hypertension is reduced post lung transplant, the right ventricle oftens returns to normal size with normal contractility.

One can determine the presence of right heart enlargement quickly by merely noting the angles needed to obtain the "best septal view" and two orthogonal views (RAO and left lateral). Normally, the best septal view is obtained at approximatley 35° LAO with subsequent 45° orthogonal views at 10° RAO and 80° LAO. In this case, the initial study shows significant leftward (counterclockwise) rotation of the heart with the best septal view at 60° LAO, and orthogonal views at 15° LAO and "105° LAO" (or 75° LPO). With left heart enlargement, the heart rotates rightward and the best septal view will shift toward a more shallow LAO.

Differential Diagnosis List

Other causes of increased pulmonary artery systolic pressure or increased pulmonary vascular resistance such as :

1) Chronic pulmonary embolus

2} Pulmonary fibrosis

3) Atrial septal defect with Eisenmenger's physiology (expect to also see left atrial enlargement)

4} Severe mitral stenosis (expect to also see left atrial enlargement)

5) Pulmonic stenosis (less common cause)

ACR Codes and Keywords:

References and General Discussion of Cardiac Blood Pool Scintigraphy (Anatomic field:Heart and Great Vessels, Category:Misc)

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Case number: ca003

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