Early impairment of myocardial deformation assessed by regional speckle-tracking echocardiography in the indeterminate form of Chagas disease without fibrosis detected by cardiac magnetic resonance

Abstract

Chagas disease (CD) will account for 200,000 cardiovascular deaths worldwide over the next 5 years. Early detection of chronic Chagas cardiomyopathy (CCC) is a challenge. We aimed to test if speckle-tracking echocardiography (STE) can detect incipient myocardial damage in CD.

Methods: Among 325 individuals with positive serological tests, 25 (age 55±12yrs) were selected to compose the group with indeterminate form of Chagas disease (IFCD), based on stringent criteria of being asymptomatic and with normal EKG/X-ray studies. This group was compared with a group of 20 patients with CCC (55±11yrs) and a group of 20 non-infected matched control (NC) subjects (48±10yrs). CD patients and NC were submitted to STE and CD patients were submitted to cardiac magnetic resonance (CMR) with late gadolinium administration to detect cardiac fibrosis by the late enhancement technique. Global longitudinal strain (GLS), circumferential (GCS) and radial strain (GRS) were defined as the average of segments measured from three apical view (GLS) and short axis views (GRS and GCS). Regional left ventricular (LV) longitudinal strain (Reg LS) was measured from each of the 17 segments. Twist was measured as systolic peak difference between basal and apical rotation and indexed to LV length to express torsion.

Results: STE global indices (GLS, GCS, twist and torsion) were reduced in CCC vs NC (GLS: -14±6.3% vs -19.3±1.6%, p = 0.001; GCS: -13.6±5.2% vs -17.3 ±2.8%; p = 0.008; twist: 8±7° vs 14±7°, p = 0.01 and torsion: 0.96±1°/cm vs 1.9±1°/cm, p = 0.005), but showed no differences in IFCD vs NC. RegLS was reduced in IFCD vs NC in four LV segments: basal-inferior (-16.3±3.3% vs -18.6±2.2%, p = 0.013), basal inferoseptal (-13.1±3.4 vs -15.2±2.7, p = 0.019), mid-inferoseptal (-17.7±3.2 vs -19.4±2, p = 0.032) and mid-inferolateral (-15.2±3.5 vs -17.8±2.8, p = 0.014). These abnormalities in RegLS occurred in the absence of myocardial fibrosis detectable with CMR in nearly 92% of subjects with IFCD, while myocardial fibrosis was present in 65% with CCC.

Conclusion: RegLS detects early regional impairment of myocardial strain that is independent from fibrosis in IFCD subjects.

Fig 1. Flowchart of selection of Indeterminate Form Chagas Disease (IFCD) group of individuals with Chagas positive serologies.

Fig 2. Global strain from LV (GLS, GCS, GRS) and RV (free wall) GLS in IFCD and CCC groups.

Fig 2 shows median values of each studied group (NC, IFCD and CCC) of LV GLS, GCS, GRS and RV GLS. All indexes of LV and RV global deformation express a tendency of reduction from NC to IFCD and to CCC. IFCD = Indeterminate Form of Chagas disease; CCC = Chronic Chagas cardiomyopathy; LV = left ventricle; RV = right ventricle; GLS = global longitudinal strain; GCS = global circumferential strain; GRS = global radial strain. p-value of comparison between NC vs IFCD.

Fig 3. LV Twist (panel A) and torsion (panel B) between groups.

Fig 3 depicts median values of twist (panel A) and torsion (panel B) with a tendency of reduction from NC to IFCD and to CCC. p-value of comparison between NC vs IFCD.

Fig 4. Correlation between myocardium percentage of fibrosis and GLS in patients with CD.

Dotted line marks the clinical lower limit of normality of GLS for this software.

Fig 5. Illustrative examples of subjects with IFCD (panel A and B) and CCC (panels C and D).

Panels A and C show RegLS in a bulls-eye representation. Inferior panels (B and D) represent wall motion values (left) and hyper-enhancement (fibrosis) at right. This IFCD subject (panel A and B) shows reduced RegLS even without myocardial fibrosis in LGE. CCC subject (C and D) shows worse RegLS values and there is a topographic correlation with fibrosis.