Page 8 - Read Online

Page 2 of 11 Genovesi et al. Vessel Plus 2021;5:50 https://dx.doi.org/10.20517/2574-1209.2021.67

myocardial metabolism; and the presence of amyloid deposits. The diagnosis of cardiac amyloidosis
requires the evaluation of clinical and bio-humoral parameters a series of instrumental evaluations, and
often a bioptic confirmation, sometimes by endomyocardial biopsy.

For the diagnosis of transthyretin cardiac amyloidosis (ATTR), it is now possible to perform a scintigraphic
evaluation using bone-seeking radiopharmaceuticals labeled with metastable technetium 99 (99mTc-PYP,
99mTc-DPD, and 99mTc-HMDP); this approach, when a monoclonal disease is excluded, allows a
definitive diagnosis without the need for a histological examination.

When the scintigraphy with osteotropic radiopharmaceuticals is negative or in the presence of a
monoclonal disease, the definitive diagnosis of cardiac amyloidosis cannot be reached without performing
further instrumental investigations and eventually with a bioptic confirmation.

In the last 10 years, the development of new PET radiopharmaceuticals for the detection of amyloid deposits
has opened a new path for the differential diagnosis of cardiac amyloidosis.

VENTRICULAR PERFUSION
Patients with cardiac amyloidosis (CA) can have anginal symptoms in the absence of coronary artery
disease, as amyloid deposition leads to alterations of the endothelial function and microvascular dysfunction
before the onset of pseudo-hypertrophy. Cardiac scintigraphy with Thallium-201 (201Tl) and 99mTc-
labeled radiopharmaceuticals (Sestamibi and Tetrofosmin) is a very accurate diagnostic tool of wide clinical
use for the evaluation of myocardial perfusion and viability, but its use in CA has been limited to a few
[1,2]
observations . Myocardial bone-seeking radiotracer uptake has been observed in a patient without any
scintigraphic evidence of myocardial ischemia and with impaired ejection-fraction , suggesting that
[3]
[4]
combined imaging may be useful in assessing the extent of organ damage. Kodama et al. evaluated 5
patients with CA and 12 control subjects by 201Tl cardiac scintigraphy, demonstrating that myocardial
regions affected by amyloid deposition are characterized by a mixture of viable and necrotic tissue; 210Tl
washout was significantly increased in CA patients compared to control subjects, particularly in 4 patients
who died within a year. The less evidence for the use of perfusion scintigraphy in the evaluation of patients
with CA explains its limited clinical use in this kind of patients.

VENTRICULAR FUNCTION
The first nuclear image of CA was obtained in 1968 by Wolfgang Hauser; the author performed a radio-
isotopic ventriculography [blood pool gating (BPG)] with 99mTc-labeled serum albumin in a patient with
autoptic diagnosis of CA. BPG was used for the identification of pericardial effusion, and the researcher
noticed that the patient showed an increased inter-ventricular septum thickness which was described as a
[5]
scintigraphic sign of infiltrative heart disease . BPG can provide other parameters such as times and rates of
ventricular filling and emptying; these parameters have been used in the differential diagnostics between
cardiac and pericardial restrictive pathologies. Gerson et al. observed that patients with pericardial
[6]
constriction showed higher peak filling rate values when compared to patients with restrictive heart disease.
Hongo et al. used BPG to evaluate left ventricular diastolic function in 17 patients with familial
[7]
polyneuropathy, demonstrating a lower peak filling rate associated with a significant delay in ventricular
filling when compared to a control group. More recently, Clements et al. evaluated the differences in
[8]
ventricular filling rate among three groups of patients with pulmonary disease, cardiac amyloidosis, and
pericarditis and a control group, concluding that variations in ventricular filling rate can be used for
differential diagnosis. Nowadays, gated-SPECT with 99mTc-Tetrofosmin or 99mTc-Sestamibi is a widely
used technique to obtain perfusion and function parameters, and it also allows obtaining data on diastolic