A primary isolated heart model of Takotsubo syndrome for mechanistic investigation and preclinical therapeutic testing

Figures

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  Figure 1. Schematic of the primary isolated heart TTS model. Langendorff perfusion system with constant-pressure perfusion, intra-aortic isoprenaline infusion port, and high-resolution ultrasound imaging for real-time functional assessment. Hearts were monitored continuously for 6 h following catecholamine exposure.

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  Figure 2. Comprehensive haemodynamic characterization of the primary isolated heart TTS phenotype. Time-series trajectories (mean ± 95% confidence intervals) of 12 continuously recorded haemodynamic parameters over 360 min in control (n = 10) and primary isolated heart TTS (n = 10) hearts. Following intra-aortic isoprenaline administration, primary isolated heart TTS hearts exhibited an initial hyperdynamic response followed by progressive deterioration of systolic function, diastolic relaxation, myocardial work, and coronary perfusion compared with controls, illustrating coordinated evolution of the TTS-like phenotype. Abbreviations: HR, heart rate; LVSP, left ventricular systolic pressure; LVEDP, left ventricular end-diastolic pressure; LVDP, left ventricular developed pressure; dP/dtmax, maximum rate of pressure development; dP/dtmin, minimum rate of pressure decline; TAU, isovolumic relaxation constant (calculated using the predefined surrogate described in Methods); RPP, rate-pressure product; CF, coronary flow; CVR, coronary vascular resistance; eDT, estimated developed tension; rRPP, relative rate-pressure product.

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  Figure 3. Generalized additive mixed model (GAMM) analysis demonstrates the triphasic evolution of the primary isolated heart TTS phenotype. GAMM-fitted trajectories (mean ± 95% confidence intervals) for heart rate (HR), left ventricular developed pressure (LVDP), isovolumic relaxation constant (TAU), and coronary flow (CF) in control (green, n = 10) and primary isolated heart TTS (red, n = 10). The fitted trajectories identify three reproducible physiological phases following catecholamine exposure: an initial hyperactivation phase (0–60 min), a transition phase (60–240 min), and a functional nadir phase (240–360 min), characterized by progressive impairment of contractility, relaxation, and coronary perfusion. The group-by-time interaction was significant for all parameters shown.

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  Figure 4. First-derivative analysis of GAMM-fitted trajectories identifies temporal changes in the primary isolated heart TTS phenotype. First derivatives of the fitted GAMM smooths for heart rate, left ventricular developed pressure, isovolumic relaxation constant (TAU), and coronary flow in control and primary isolated TTS hearts. Solid blue lines represent control hearts, and dashed orange lines represent primary isolated TTS hearts; shaded regions indicate 95% confidence intervals. Positive derivative values indicate an increasing fitted trajectory, negative values indicate a decreasing trajectory, and crossings of zero indicate changes in trajectory direction. Background regions denote the predefined hyperactivation (0–60 min), transition (60–240 min), and functional nadir (240–360 min) phases. Coordinated changes across the four physiological domains supported approximate transition points at 60 and 240 min. The derivative analyses were exploratory and were used to characterize temporal patterning rather than establish biological mechanisms.

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  Figure 5. Representative echocardiographic cine loops demonstrating apical ballooning. High-resolution echocardiography with speckle-tracking strain analysis in parasternal long-axis view. (A) Control heart showing synchronous contraction with uniform strain distribution. (B) Secondary isolated heart TTS (in vivo induction, ex vivo perfusion) demonstrating mechanical dyssynchrony and regional wall-motion abnormality. (C) Primary isolated heart TTS showing characteristic apical akinesia, mechanical dyssynchrony, and regional wall-motion abnormality, the hallmark TTS phenotype induced entirely within the isolated preparation.

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  Figure 6. Quantitative echocardiographic characterization of the catecholamine-induced TTS-like phenotype. (A–C) Individual changes in ejection fraction (EF) from baseline to 6 h in control, primary isolated heart TTS, and secondary isolated heart TTS preparations, respectively. Thin lines represent individual hearts, and thick lines with error bars represent group mean ± SEM (n = 6 per group). Baseline EF was comparable across groups; control hearts showed a modest decline over 6 h, whereas both TTS groups demonstrated marked reductions in EF. ***P < 0.001 vs. baseline within the same group using (Annova). (D) Global longitudinal strain (GLS) and (E) left ventricular akinesia index (LVAI) at 6 h in control, primary isolated heart TTS, and secondary isolated heart TTS hearts. Boxplots show median and interquartile range, and superimposed points represent individual hearts. Less negative GLS values indicate impaired systolic deformation. Both TTS groups exhibited less negative GLS and increased LVAI compared with control hearts, demonstrating impaired global systolic deformation together with regional apical dysfunction. Statistical comparisons were performed using Annova and Tukey post hoc…