HUMAN 3D CARDIAC SAFETY
& Cardiotoxicity testing
Detect cardiac liabilities. Understand their functional impact.
Assess how your compounds affect cardiac contractility, electrophysiology, repolarization and calcium handling with SmartHeart®, 4Dcell's human 3D cardiac testing platform.
Our cardiac safety studies combine quantitative tissue-level measurements with scientific interpretation to help pharmaceutical and biotechnology teams investigate cardiac liabilities, understand drug-induced functional changes and support compound selection.
Beyond ion-channel screening: investigate cardiac function
Drug-induced cardiotoxicity can result from multiple mechanisms, including altered repolarization, disrupted calcium handling, abnormal beating activity and impaired cardiac contractility.
While conventional ion-channel assays provide essential mechanistic information, they do not directly characterize the integrated functional response of cardiac tissue.
SmartHeart® uses self-assembled, ring-shaped 3D microtissues combining human iPSC-derived cardiomyocytes and cardiac fibroblasts. The platform enables quantitative analysis of cardiac mechanical activity, with complementary electrophysiological and calcium-handling measurements.
These functional readouts help investigate how compound-induced molecular effects translate into measurable changes in cardiac tissue behavior.
Human 3D cardiac safety assays
Electrophysiology & proarrhythmic risk assessment
Investigate drug-induced alterations in cardiac electrical activity and repolarization.
SmartHeart® supports optical action potential measurements using voltage-sensitive fluorescence imaging to characterize electrophysiological responses in human 3D cardiac microtissues.
Key readouts
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Action potential duration (APD) and repolarization kinetics
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Action potential amplitude and upstroke characteristics
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Depolarization and repolarization changes
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Beating frequency and rhythm irregularity
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Concentration-dependent electrophysiological responses
Applications
Investigation of ion-channel-related cardiac liabilities, altered repolarization and electrophysiological mechanisms associated with proarrhythmic risk, including those relevant to QT prolongation and torsade de pointes (TdP).
Optical APD measurements provide mechanistic information on cardiac electrical behavior and are not equivalent to clinical ECG-derived QT/QTc intervals.
Dofetilide-induced changes in action potential duration (APD10, APD50 and APD90) in SmartHeart® human 3D cardiac microtissues. The concentration-dependent increase in APD90 reflects delayed cardiac repolarization, a key electrophysiological marker associated with proarrhythmic risk.
Calcium handling & excitation–contraction coupling
Explore calcium-dependent mechanisms underlying cardiac functional changes.
Intracellular calcium dynamics regulate cardiac excitation–contraction coupling and influence both electrical activity and mechanical contraction.
Complementary fluorescence-based calcium transient measurements can be incorporated to investigate drug-induced changes in calcium handling.
Key readouts
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Calcium transient amplitude
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Calcium rise and decay kinetics
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Calcium transient duration
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Beating frequency and regularity
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Concentration-dependent calcium responses
Applications
Mechanistic investigation of compound-induced changes in calcium cycling, excitation–contraction coupling and calcium-dependent cardiac dysfunction.
Calcium-handling studies are designed according to the experimental objective, with study conditions and assay performance assessed for the intended application.
Cardiac contractility & inotropic safety
Detect unwanted positive or negative inotropic effects during drug development.
Drug candidates can impair cardiac mechanical function independently of major electrophysiological abnormalities.
The SmartHeart® Contractility Assay quantifies the contraction of human cardiac microtissues using brightfield video analysis and automated tissue tracking.
Key readouts
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Contraction strain and derived contractile stress
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Maximum and mean contraction speed
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Maximum and mean relaxation speed
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Contraction and relaxation timing
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Beating frequency and regularity
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Concentration–response profiles and EC50/IC50 estimates when supported by the data
Applications
Detection and characterization of unwanted positive or negative inotropy, altered contraction or relaxation kinetics, and drug-induced functional cardiac liabilities during drug discovery and lead optimization.
The core SmartHeart® Contractility Assay has undergone fit-for-purpose qualification using seven reference compounds with established positive or negative inotropic effects.
Concentration-dependent negative inotropic effect of itraconazole in SmartHeart® human 3D cardiac microtissues. Increasing drug concentrations progressively reduce contraction strain, demonstrating the assay's ability to detect drug-induced impairment of cardiac contractile function (n = 42 microtissues, N = 3 independent experiments).
Chronic & delayed cardiotoxicity
Investigate cardiac effects that may emerge beyond acute compound exposure.
Some drug-induced cardiac liabilities develop gradually or depend on repeated exposure and may not be fully characterized by an acute functional assay.
4Dcell can develop tailored longer-duration or repeated-exposure studies to investigate delayed changes in cardiac tissue function.
Potential endpoints
Time-dependent changes in contractility and beating activity
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Functional responses following repeated compound exposure
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Tissue morphology and structural integrity
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Recovery or reversibility following compound withdrawal
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Complementary viability, imaging or molecular measurements
Applications
Investigation of delayed or cumulative cardiotoxicity, persistent functional changes and exposure-dependent cardiac responses.
Longer-duration studies are developed on a fit-for-purpose basis. Experimental conditions, relevant endpoints and performance requirements are established for each project.
Electrophysiological assessment of CiPA reference compounds
SmartHeart® has been evaluated using seven reference compounds from the Comprehensive in vitro Proarrhythmia Assay (CiPA) panel, covering different torsade de pointes (TdP) risk categories and pharmacological mechanisms.
The studies demonstrated compound-specific effects on action potential characteristics, repolarization and cardiac mechanical activity.
Dofetilide — High TdP-risk reference compound
Dofetilide, an IKr potassium-channel blocker, induced substantial prolongation of late action potential repolarization, with more than a twofold increase in APD50–90 metrics.
These electrophysiological changes were accompanied by reduced beating frequency and contractile activity. At the highest tested concentration, up to 38% of cardiac rings became quiescent.
Ranolazine — Multichannel pharmacology
Ranolazine produced a more complex electrophysiological response, including changes in action potential amplitude, depolarization kinetics and moderate late-repolarization prolongation.
These findings illustrate how tissue-level measurements can capture distinct pharmacological responses associated with different ion-channel mechanisms.
The full cardiac toxicity white paper reports nine cardioactive compounds, including seven CiPA reference drugs, with experimental conditions, concentrations, sample sizes and supporting data.
These results support mechanistic investigation of drug-induced electrophysiological and functional changes. They do not establish a clinically validated TdP risk prediction classifier or regulatory qualification of the platform.
Compound-specific cardiac responses measured with SmartHeart. Isoprenaline induces a dose-dependent increase in cardiac contractility (EC50 = 35.7 nM), while ranolazine is evaluated through electrophysiological readouts, including action potential amplitude, APD50 and the proportion of quiescent tissues.
Fit-for-purpose qualification of the SmartHeart® Contractility Assay
The SmartHeart® Contractility Assay was evaluated using seven reference compounds with known positive or negative inotropic activity and different mechanisms of action.
The assay correctly identified the expected direction of the inotropic effect for all seven tested compounds.
Five positive inotropes
Isoproterenol, Bay K 8644, omecamtiv mecarbil, istaroxime and phenylephrine.
Two negative inotropes
Itraconazole and quinidine.
The qualification study included three independent experiments per compound, with at least 20 evaluable cardiac microtissues per compound across the experiments.
Assay performance was characterized through concentration–response analysis, ring-to-ring and experiment-to-experiment variability, and readout-specific detection sensitivity.
Under the qualified study design, the estimated minimum detectable effect ranged from 3.7% to 5.7% of baseline, depending on the readout, at 80% statistical power and a 5% significance level.
These results support the use of the SmartHeart® Contractility Assay for detecting and characterizing drug-induced inotropic responses within its qualified operating conditions.
The qualification applies to the tested acute exposure workflow and should not be extrapolated automatically to other cell compositions, exposure conditions or measurement endpoints.
For additional examples of compound-specific positive inotropic responses, explore our SmartHeart® inotropy white paper.
Dose-dependent positive and negative inotropic responses in SmartHeart human 3D cardiac microtissues. Bay K 8644 increases contraction strain, while itraconazole produces a concentration-dependent decrease. Both responses were characterized across three independent experiments, demonstrating SmartHeart's ability to detect opposite pharmacological effects on cardiac contractility.
Experimental evidence supporting SmartHeart® cardiac safety testing
From cardiac safety question to quantitative results
1. Define your cardiac safety question
We work with your team to identify the potential cardiac liability, the compound's expected pharmacology and the functional endpoints needed to address your research question.
2. Design your experiment
The experimental strategy is tailored to the compound and study objectives, including concentration range, exposure duration, control conditions, selected readouts and qualification requirements.
3. Measure cardiac functional responses
Compound-induced changes are assessed using the selected combination of contractility, electrophysiological, calcium-handling or complementary measurements.
4. Analyze and interpret the results
4Dcell provides quantitative data, quality-control information, concentration–response analysis and scientific interpretation within the defined experimental scope and method limitations.
5. Deliver the Scientific Report
We provide the agreed quantitative results, study methods, quality-control information, scientific interpretation and relevant limitations to support evaluation of the compound's cardiac safety profile.
Why choose SmartHeart® for cardiac safety testing?
Integrated human 3D cardiac tissue
SmartHeart® combines human iPSC-derived cardiomyocytes and cardiac fibroblasts in self-assembled, ring-shaped 3D microtissues. This multicellular architecture enables coordinated tissue contraction and integrated functional assessment beyond isolated cellular responses.
Quantitative functional measurements
SmartX™ Analysis extracts cardiac contractility metrics from brightfield recordings, including tissue deformation, derived contractile stress, contraction and relaxation kinetics, and beating activity.
Scalable 96-well format
SmartHeart® combines tissue-level functional measurements with a standard 96-well plate format, supporting concentration–response studies, parallel compound testing and integration into preclinical drug discovery workflows.
Nine microtissues per well for robust functional data
Each SmartHeart® well contains nine individual cardiac microtissues, providing multiple tissue-level measurements under the same experimental conditions. This unique architecture enables assessment of within-well variability, supports tissue-level quality control and strengthens the interpretation of compound-induced functional responses.
Complementary cardiac readouts
Contractility measurements can be complemented by electrophysiological and calcium-handling assays when additional mechanistic information is required.
Flexible study design & scientific support
4Dcell scientists help define study conditions, experimental controls, readouts, quality-control requirements and data interpretation according to the compound and research objective.
Frequently Asked Questions
Discuss your cardiac safety testing project
Investigate potential cardiac liabilities with human 3D functional data.
Whether you need to characterize an unexpected inotropic effect, investigate a repolarization-related safety signal or develop a tailored cardiotoxicity study, our scientists can help define an experimental strategy matched to your compound and research objectives.