Clinical characteristics and prognosis of cardiac amyloidosis defined by mass spectrometry-based proteomics in an Australian cohort.

BACKGROUND: Cardiac amyloidosis has a very poor prognosis, but it is the nature of the involved precursor protein that ultimately dictates treatment and survival. AIM: Definitively characterise the amyloid subtype by mass spectrometry (MS) in an Australian cohort of patients with cardiac amyloidosis. METHODS: We report the clinical characteristics and survival of 47 cardiac amyloid patients across two Australian centres including 39 patients evaluated for definitive amyloid subtype utilising laser microdissection and tandem mass spectrometry. RESULTS: A quarter (n = 12) of patients were classified as wild-type transthyretin amyloidosis (ATTRwt), 33 patients as light or heavy chain amyloidosis (AL or AH) and two as hereditary mutant transthyretin amyloidosis. Greater left ventricular hypertrophy (interventricular septum 22 vs 15 mm; P = 0.005) and history of cardiac arrhythmia (75% vs 31%; P = 0.016) were significantly associated with ATTRwt patients compared with AL/AH patients. AL patients demonstrated significantly shorter median survival compared with ATTRwt patients (3.5 vs 37 months; P = 0.007). New York Heart Association class III-IV symptoms or plasma cells ≥10% at diagnosis, were the only independent predictors of worse survival in AL patients on multivariate analysis. CONCLUSIONS: AL amyloidosis accounted for 68% of our cohort of patients with cardiac amyloidosis while ATTR accounted for 26%. In the era of novel therapies for both AL amyloid and ATTR, identification of the correct amyloid subtype is essential in making therapeutic decisions and providing accurate prognostic information to patients. Laser microdissection and tandem mass spectrometry plays an important role in identifying amyloid subtype, particularly in complex cases.

Irreversible triggers for hypertrophic cardiomyopathy are established in the early postnatal period.

BACKGROUND: Hypertrophic cardiomyopathy (HCM) is caused by mutations in sarcomere protein genes, and left ventricular hypertrophy (LVH) develops as an adaptive response to sarcomere dysfunction. It remains unclear whether persistent expression of the mutant gene is required for LVH or whether early gene expression acts as an immutable inductive trigger. OBJECTIVES: The aim of this study was to use a regulatable murine model of HCM to study the reversibility of pathological LVH. METHODS: The authors generated a double-transgenic mouse model, tTAxαMHCR403Q, in which expression of the HCM-causing Arg403Gln mutation in the α-myosin heavy chain (MHC) gene is inhibited by doxycycline administration. Cardiac structure and function were evaluated in groups of mice that received doxycycline for varying periods from 0 to 40 weeks of age. RESULTS: Untreated tTAxαMHCR403Q mice showed increased left ventricular (LV) mass, contractile dysfunction, myofibrillar disarray, and fibrosis. In contrast, mice treated with doxycycline from conception to 6 weeks had markedly less LVH and fibrosis at 40 weeks. Transgene inhibition from 6 weeks reduced fibrosis but did not prevent LVH or functional changes. There were no differences in LV parameters at 40 weeks between mice with transgene inhibition from 20 weeks and mice with continuous transgene expression. CONCLUSIONS: These findings highlight the critical role of the early postnatal period in HCM pathogenesis and suggest that mutant sarcomeres manifest irreversible cardiomyocyte defects that induce LVH. In HCM, mutation-silencing therapies are likely to be ineffective for hypertrophy regression and would have to be administered very early in life to prevent hypertrophy development.

Effects of mechanical stress and carvedilol in lamin A/C-deficient dilated cardiomyopathy.

RATIONALE: Mutations in the LMNA gene, which encodes the nuclear lamina proteins lamin A and lamin C, are the most common cause of familial dilated cardiomyopathy (DCM). Mechanical stress-induced apoptosis has been proposed as the mechanism underpinning DCM in lamin A/C-deficient hearts, but supporting in vivo evidence has been lacking. OBJECTIVE: Our aim was to study interventions to modify mechanical stress in heterozygous Lmna knockout (Lmna(+/-)) mice. METHODS AND RESULTS: Cardiac structure and function were evaluated before and after exercise training, thoracic aortic constriction, and carvedilol treatment. Lmna(+/-) mice develop adult-onset DCM with relatively more severe disease in males. Lmna(+/-) cardiomyocytes show altered nuclear morphology and perinuclear desmin organization, with enhanced responses to hypo-osmotic stress indicative of cytoskeletal instability. Despite these structural defects that provide a template for mechanical stress-induced damage, young Lmna(+/-) mice subjected to 6 weeks of moderate or strenuous exercise training did not show induction of apoptosis or accelerated DCM. In contrast, regular moderate exercise attenuated DCM development in male Lmna(+/-) mice. Sustained pressure overload generated by thoracic aortic constriction depressed ventricular contraction in young wild-type and Lmna(+/-) mice with no sex or genotype differences in the time-course or severity of response. Treatment of male Lmna(+/-) mice from 12 to 40 weeks with the beta-blocker, carvedilol, prevented the dilatation and contractile dysfunction that was observed in placebo-treated mice. CONCLUSIONS: These data suggest that factors other than mechanical stress-induced apoptosis contribute to DCM and provide the first demonstration that regular moderate exercise and carvedilol can modify disease progression in lamin A/C-deficient hearts.

Association of minimal rejection in lung transplant recipients with obliterative bronchiolitis.

The clinical significance of minimal acute rejection (grade A1) in lung transplant recipients is unknown. We prospectively analyzed 1,159 transbronchial lung biopsies in 184 patients. Two hundred seventy-nine biopsies in 128 participants confirmed A1 histology at a mean postoperative day of 229 +/- 340. Sixty four of 255 surveillance A1 lesions progressed to high-grade acute rejection by 3 months of follow-up, whereas 40 developed new lymphocytic bronchiolitis. Twenty-four A1 biopsies were symptomatic, with only two cases progressing to high-grade rejection after steroid therapy. Seventy-eight of 184 patients experienced multiple (> or = 2) A1 biopsies in the first 12 months after transplant. Bronchiolitis obliterans syndrome developed in 68% of patients with multiple A1 lesions at a mean of 599 +/- 435 days, compared with 43% of patients with one or less A1 lesions at a mean of 819 +/- 526 (p = 0.022). Eighteen patients experienced multiple A1 biopsies after transplant in the absence of high-grade rejection episodes yet also developed earlier obliterative bronchiolitis (456 +/- 245 days, p = 0.020). We conclude that for A1 transbronchial lung biopsies, the conventional treatment of observation only is now challenged even in patients who are asymptomatic. Patients who experience multiple A1 lesions develop an earlier onset of obliterative bronchiolitis and may warrant alternative immunosuppressive strategies.

Treated cytomegalovirus pneumonia is not associated with bronchiolitis obliterans syndrome.

The association of cytomegalovirus (CMV) infection with the development of bronchiolitis obliterans syndrome (BOS) is unclear. We studied 341 lung transplant recipients to assess whether histopathologically diagnosed CMV pneumonia treated with ganciclovir was a risk factor for development of BOS and patient survival. We also analyzed the relationship between CMV donor/recipient serologic status and BOS plus the temporal association between acute rejection and CMV pneumonia. Freedom from BOS for patients with (n = 151) and without (n = 190) CMV pneumonia was 83 and 90% (1 year), 52 and 56% (3 years), and 29 and 38% (5 years), respectively (p = 0.2660). Cumulative survival of patients with and without CMV pneumonia was 90 and 93% (1 year), 70 and 74% (3 years), and 58 and 63% (5 years), respectively (p = 0.1811). There were no significant differences in either development of BOS or patient survival with any combination of donor/recipient serostatus for CMV. Acute rejection occurred in the month preceding CMV pneumonia in 62 of 193 (32%) cases. Histopathologically confirmed CMV pneumonia treated with ganciclovir is not a risk factor for BOS or patient survival, nor is any particular CMV serologic donor/recipient group. CMV pneumonia often follows acute rejection, perhaps as a result of augmented immunosuppression.

Defects in nuclear structure and function promote dilated cardiomyopathy in lamin A/C-deficient mice.

Laminopathies are a group of disorders caused by mutations in the LMNA gene that encodes the nuclear lamina proteins, lamin A and lamin C; their pathophysiological basis is unknown. We report that lamin A/C-deficient (Lmna(-/-)) mice develop rapidly progressive dilated cardiomyopathy (DCM) characterized by left ventricular (LV) dilation and reduced systolic contraction. Isolated Lmna(-/-) myocytes show reduced shortening with normal baseline and peak amplitude of Ca(2+) transients. Lmna(-/-) LV myocyte nuclei have marked alterations of shape and size with central displacement and fragmentation of heterochromatin; these changes are present but less severe in left atrial nuclei. Electron microscopy of Lmna(-/-) cardiomyocytes shows disorganization and detachment of desmin filaments from the nuclear surface with progressive disruption of the cytoskeletal desmin network. Alterations in nuclear architecture are associated with defective nuclear function evidenced by decreased SREBP1 import, reduced PPARgamma expression, and a lack of hypertrophic gene activation. These findings suggest a model in which the primary pathophysiological mechanism in Lmna(-/-) mice is defective force transmission resulting from disruption of lamin interactions with the muscle-specific desmin network and loss of cytoskeletal tension. Despite severe DCM, defects in nuclear function prevent Lmna(-/-) cardiomyocytes from developing compensatory hypertrophy and accelerate disease progression.

Prospective analysis of 1,235 transbronchial lung biopsies in lung transplant recipients.

OBJECTIVE: Fiber-optic bronchoscopy with multiple transbronchial lung biopsies (TBB) is the gold standard of evaluation of the pulmonary allograft post-lung transplantation (LT). However, controversy exists regarding the need for surveillance procedures and number of biopsy specimens required for satisfactory yield. The potential morbidity in obtaining multiple TBB specimens remains poorly described. We report the largest series of TBB in LT recipients to date, highlighting the occurrence of acute rejection and infection for surveillance and diagnostic procedures. The safety of TBB is analyzed and a biopsy schedule proposed. METHODS: Prospective analysis of 1,235 TBB in 230 LT recipients performed at St Vincent's Hospital from January 1995 to June 2000. RESULTS: Eight hundred thirty-six (67.7%) TBB were performed as surveillance and 399 (32.3%) for a clinical indication. No significant acute rejection (AR) or infection was disclosed in 53.3% of procedures. The Lung Rejection Study Group requirement of at least five pieces of evaluable lung parenchyma was achieved in 98.2% of procedures. The average number of evaluable fragments per procedure was 6.4, whereas only 3 TBB (0.24%) contained no lung parenchyma and 44 (3.6%) no bronchial wall. Histologic features of AR, lymphocytic bronchiolitis or infection were found in 18.9% of surveillance and 86.4% of clinical TBBs. The yield of surveillance procedures between 4 and 12 months was just 1.1% for cytomegalovirus and 6.1% for AR. The overall complication rate was 6.35% with no deaths recorded. CONCLUSION: Taking 10 to 12 TBB specimens has a high diagnostic yield and rarely fails to provide adequate tissue. The role of surveillance procedures post-lung transplantation remains controversial.