B-Type Natriuretic Peptide (BNP) and Mitral Velocity E/A Ratio (MV E/A) Are Two Important Noninvasive Functional Indices of Cardiac AL Amyloidosis.

Cardiac AL amyloidosis is characterized as global myocardial dysfunction, oftentimes complicated by pulmonary events during stem cell mobilization and autotransplant. Although BNP or N terminal proBNP has been shown to be prognostically significant for survival following autotransplant, pathophysiologic processes of the heart for elevated levels of these molecules are unclear. In the current study, we sought to evaluate functional cardiac indices assessed by two-dimensional and Doppler echocardiography and to correlate to BNP and clinical events. Evaluations were done on 39 serial echocardiogrmas obtained between July 2006 and July 2007 from 5 patients with established cardiac AL amyloidosis as a part of systemic amyloidosis (3 primary; 2 secondary to free kappa light chain multiple myeloma). Their median age was 78 years (range 48 to 80). One patient presented with pulmonary edema initially and three others developed pulmonary edema (n = 2) or congestion with pleural effusion (n = 1) during the course of therapy. Two patients underwent melphalan-based autotransplant, and three received melphalan 50 mg/m² up to 2 cycles every 3 months without stem cell infusion. The median BNP at diagnosis was 1110 pg/mL (range, 115 to 2540); right ventricular diastolic diameter (RVDd) 3.8 cm (2.9 to 4.0); left ventricular end diastolic volume (LVEDV) 88 mL (50 to 125); ejection fraction 60% (53 to 77); MV E/A 2 (1.3 to 2.9); right ventricular systolic pressure (RVSP) 48 mmHg (40 to 68). In multiple regression analyses, BNP levels were most significantly correlated to the RVDd, β = 0.58, p < 0.05. The RVSP as a surrogate index of pulmonary arterial pressure was shown most dependent on the left ventricular diastolic filling assessed by the MV E/A (β = 0.93, p < 0.05) that in turn was dependent on the LVEDV (β = 2.68, p < 0.05). None of the myocardial wall measurements and left ventricular indices except these were found to be significant. Although the RVDd was dependent on the RVSP (β = −1.17, p < 0.05), both BNP and RVSP were independent of each other (β = −0.25, p = 0.6). RVSP levels were significantly elevated in 4 patients who had pulmonary complications: 50, 55, 57, 68 mmHg, respectively. The MV E/A was elevated at or above 2.5 at the time of these episodes: 2.5, 2.9, 2.9, 3.7, respectively. Decrease in both BNP and RVSP appeared to be minimally related to improving serum free light chain levels following therapy: β = 0.29, p = 0.08 and β = 0.34, p = 0.05, respectively. There was no correlation between the MV E/A and serum free light chain level either, β = 0.19, p = 0.3. The data suggests that the MV E/A and RVSP may be useful indices for monitoring patients for potential pulmonary complications, and the BNP appears to reflect more of the right-sided heart events. Further studies are needed to confirm the current findings.