Implementation of an epicardial implantable MEMS sensor for continuous and real-time postoperative assessment of left ventricular activity in adult minipigs over a short- and long-term period.

The sensing of left ventricular (LV) activity is fundamental in the diagnosis and monitoring of cardiovascular health in high-risk patients after cardiac surgery to achieve better short- and long-term outcome. Conventional approaches rely on noninvasive measurements even if, in the latest years, invasive microelectromechanical systems (MEMS) sensors have emerged as a valuable approach for precise and continuous monitoring of cardiac activity. The main challenges in designing cardiac MEMS sensors are represented by miniaturization, biocompatibility, and long-term stability. Here, we present a MEMS piezoresistive cardiac sensor capable of continuous monitoring of LV activity over time following epicardial implantation with a pericardial patch graft in adult minipigs. In acute and chronic scenarios, the sensor was able to compute heart rate with a root mean square error lower than 2 BPM. Early after up to 1 month of implantation, the device was able to record the heart activity during the most important phases of the cardiac cycle (systole and diastole peaks). The sensor signal waveform, in addition, closely reflected the typical waveforms of pressure signal obtained via intraventricular catheters, offering a safer alternative to heart catheterization. Furthermore, histological analysis of the LV implantation site following sensor retrieval revealed no evidence of myocardial fibrosis. Our results suggest that the epicardial LV implantation of an MEMS sensor is a suitable and reliable approach for direct continuous monitoring of cardiac activity. This work envisions the use of this sensor as a cardiac sensing device in closed-loop applications for patients undergoing heart surgery.

Prognostic value of pulmonary blood volume by first-pass contrast-enhanced CMR in heart failure outpatients: the PROVE-HF study.

Aims: Pulmonary blood volume (PBV) is a novel clinical application of cardiovascular magnetic resonance (CMR) imaging for the quantitative grading of haemodynamic congestion. In this study, we aimed to assess the prognostic value of PBV in a cohort of outpatients with chronic heart failure (HF). Methods and results: One hundred and twelve consecutive patients (91 men, 67 ± 12 years) and 53 age- and sex-matched healthy controls underwent echocardiography and contrast-enhanced CMR. PBV was calculated as the product of stroke volume and the number of cardiac cycles for an intravenous bolus of gadolinium contrast to pass through the pulmonary circulation determined by first-pass perfusion imaging. Compared with healthy controls, HF outpatients showed significantly higher PBV index (PBVI, 308 ± 92 vs. 373 ± 175, mL/m2, P = 0.012) and pulmonary transit time (6.8 ± 1.8 vs. 9.5 ± 4 s, P ≤0.001). During a median follow-up of 26 ± 17 months, 27 patients (24%) reached the composite end point of cardiovascular death, HF hospitalization, or sustained ventricular arrhythmias/appropriate implantable cardioverter-defibrillator intervention. Using a cut-off point of PBVI >492 mL/m2, corresponding to two standard deviations above the mean of healthy controls, event-free survival was significantly lower in patients with higher PBVI (P < 0.001). At multivariable-adjusted Cox regression analysis, PBVI was an independent predictor of the composite cardiovascular end point (per 10% increase hazard ratio 1.31, 95% confidence interval: 1.02-1.69, P = 0.03). Conclusions: PBVI is a novel application of perfusion CMR potentially useful to quantitatively determine haemodynamic congestion as a surrogate marker of left ventricular diastolic dysfunction. PBVI might prove to be helpful in stratifying the prognosis of asymptomatic or mildly symptomatic patients with left ventricular dysfunction.

Quantitative criteria for the diagnosis of the congenital absence of pericardium by cardiac magnetic resonance.

BACKGROUND: Congenital absence of the left ventricular pericardium (LCAP) is a rare and poorly known cardiac malformation. Cardiac Magnetic Resonance (CMR) is generally used for the diagnosis of LCAP because of its high soft tissue contrast, multiplanarity and cine capability, but the diagnosis is usually made by only qualitative criteria. The aim of the present study was to establish quantitative criteria for the accurate diagnosis of LCAP on CMR. METHODS: We enrolled nine consecutive patients affected by LCAP (mean age 26±8years, 7 males), 13 healthy controls, 13 patients with dilated cardiomyopathy (DCM), 12 patients with hypertrophic cardiomyopathy (HCM) and 13 patients with right ventricular overload (RVO). All patients underwent CMR. The whole-heart volume was measured in end-systole and end-diastole. Whole-heart volume change (WHVC), was the systo-diastolic change of volume, expressed percentage of the end-diastolic volume. The angle of clockwise-rotation of the heart was also measured in the end-diastolic phase of the axial cine stack. RESULTS: The WHVC was significantly higher in LCAP (21.9±5.4), compared to healthy subjects (8.6±2.4, p<0.001), DCM (7.1±1.8, p<0.001), HCM (9.3±2.4, p<0.001) and RVO (8±2.4, p<0.001). The clockwise-rotation was significantly higher in LCAP (76±14°) than healthy controls (40±11°, p<0.001), DCM (41±5°, p<0.001), HCM (30±6°, p<0.001) and RVO (49±8°, p<0.001). WHVC had the highest sensitivity (100%) and specificity (100%) for diagnosing LCAP, using a threshold of >13%. CONCLUSIONS: In LCAP the systo-diastolic WHVC was significantly higher than controls, DCM, HCM and RVO patients and resulted an optimal quantitative criteria for the diagnosis of LCAP.

Measurement of myocardial amyloid deposition in systemic amyloidosis: insights from cardiovascular magnetic resonance imaging.

BACKGROUND: Cardiac involvement in systemic amyloidosis is caused by the extracellular deposition of misfolded proteins, mainly immunoglobulin light chains (AL) or transthyretin (ATTR), and may be detected by cardiovascular magnetic resonance (CMR). The aim of this study was to measure myocardial extracellular volume (ECV) in amyloid patients with a novel T1 mapping CMR technique and to determine the correlation between ECV and disease severity. METHODS: Thirty-six patients with biopsy-proven systemic amyloidosis (mean age 70 ± 9 years, 31 men, 30 with AL and six with ATTR amyloidosis) and seven patients with possible amyloidosis (mean age 64 ± 10 years, six men) underwent comprehensive clinical and CMR assessment, with ECV estimation from pre- and postcontrast T1 mapping. Thirty healthy subjects (mean age 39 ± 17 years, 21 men) served as the control group. RESULTS: Amyloid patients presented with left ventricular (LV) concentric hypertrophy with impaired biventricular systolic function. Cardiac ECV was higher in amyloid patients (definite amyloidosis, 0.43 ± 0.12; possible amyloidosis, 0.34 ± 0.11) than in control subjects (0.26 ± 0.04, P < 0.05); even in amyloid patients without late gadolinium enhancement (0.35 ± 0.10), ECV was significantly higher than in the control group (P < 0.01). A cut-off value of myocardial ECV >0.316, corresponding to the 95th percentile in normal subjects, showed a sensitivity of 79% and specificity of 97% for discriminating amyloid patients from control subjects (area under the curve of 0.884). Myocardial ECV was significantly correlated with LV ejection fraction (R(2)  = 0.16), LV mean wall thickness (R(2)  = 0.41), LV diastolic function (R(2)  = 0.21), right ventricular ejection fraction (R(2)  = 0.13), N-terminal fragment of the pro-brain natriuretic peptides (R(2)  = 0.23) and cardiac troponin (R(2)  = 0.33). CONCLUSION: Myocardial ECV was increased in amyloid patients and correlated with disease severity. Thus, measurement of myocardial ECV represents a potential noninvasive index of amyloid burden for use in early diagnosis and disease monitoring.

High concentration of C-type natriuretic peptide promotes VEGF-dependent vasculogenesis in the remodeled region of infarcted swine heart with preserved left ventricular ejection fraction.

BACKGROUND: Vasculogenesis is a hallmark of myocardial restoration. Post-ischemic late remodeling is associated with pathology and function worsening. At the same time, neo-vasculogenesis helps function improving and requires the release of vascular endothelial growth factor type A (VEGF-A). The vasculogenic role of C-type natriuretic peptide (CNP), a cardiac paracrine hormone, is unknown in infarcted hearts with preserved left ventricular (LV) ejection fraction (EF). We explored whether myocardial VEGF-dependent vasculogenesis is affected by CNP. METHODS AND RESULTS: To this end, infarcted swine hearts were investigated by magnetic resonance imaging (MRI), histological and molecular assays. At the fourth week, MRI showed that transmural myocardial infarction (MI) affected approximately 13% of the LV wall mass without impairing global function (LVEF>50%, n=9). Increased fibrosis, metalloproteases and capillary density were localized to the infarct border zone (BZ), and were associated with increased expression of CNP (p=0.03 vs. remote zone (RZ)), VEGF-A (p<0.001 vs. RZ), BNP, a marker of myocardial dysfunction (p<0.01 vs. RZ) and the endothelial marker, factor VIII-related antigen (p<0.01 vs. RZ). In vitro, CNP 1000 nM promoted VEGF-dependent vasculogenesis without affecting the cell growth and survival, although CNP 100 nM or a high concentration of VEGF-A halted vascular growth. CONCLUSIONS: CNP expression is locally increased in infarct remodeled myocardium in the presence of dense capillary network. The vasculogenic response requires the co-exposure to high concentration of CNP and VEGF-A. Our data will be helpful to develop combined myocardial delivery of CNP and VEGF-A genes in order to reverse the remodeling process.