A heart that should have burst.

The hydraulic engine asks the heart for outputs that would rupture an unprepared myocardium. LERV's answer is a cardiac module: increased intermyofibrillar mitochondrial density, retuned calcium handling, and the MMP2 proteoglycan modification that lets chambers fill further without tearing. Stroke volume climbs. The organ survives a night at a duty cycle that would be a medical emergency in any other chest.

Dawn does not forgive all of it. Creatine kinase leaks. Troponin flickers. The recovery window of hours one through seventy-two is where the clinical misdiagnoses live: viral myocarditis, panic disorder, unexplained rhabdomyolysis. The heart held. The bloodwork looks like a disaster.