Supports heart function
The heart adapts to pressure by growing thicker and stiffer, and past a point that adaptation is the disease: a stiff ventricle fills badly. This is distinct from Contractility, which is how hard it pumps — this pathway is how the muscle is rebuilt.
In depth
Structural change of the heart muscle — wall thickening and fibrous scarring laid down in response to sustained load.
What drives it
Lowers blood pressure increases it.
Angiotensin II activates fibroblasts and cardiac myocytes to promote cardiac remodeling, driving maladaptive myocardial hypertrophy and fibrosis; a local intracardiac renin-angiotensin system exists and is differentially expressed in pressure-overload and post-infarction remodeling (PMC9356743; PMID 7495212). The sign depends on duration: acute RAAS activation supports perfusion in low-output states, while sustained engagement drives adverse remodeling, heart-failure progression and arrhythmogenesis. And the therapy is population-specific: RAAS blockade improves mortality and hospitalization in systolic heart failure and acute MI but has not shown the same benefit in preserved ejection fraction. Provenance: previously cited PMID 8583476 could not be confirmed and has been replaced. PMID 7495212 · PMC9356743
Reduces scarring increases it.
TGF-β is the switch that turns load into scar: myocardial TGF-β is upregulated after infarction, in cardiac hypertrophy and in dilated or hypertrophic cardiomyopathy; it transduces hypertrophic signals in cardiomyocytes and drives myofibroblast transdifferentiation with matrix deposition, and overexpression in the mouse heart produces fibrosis and hypertrophy (PMC3072437). Note — the effect is rather than simply bad: blocking TGF-β receptor signaling after pressure overload markedly reduced collagen deposition but produced greater ventricular dilation and systolic dysfunction. A baseline level appears necessary to hold the structure together. Both canonical and non-canonical TGF-beta pathways are implicated in cardiac fibrosis; TGF-beta1 induced significant myofibroblast activation and ECM dysregulation in human ventricular and atrial cardiac myofibroblasts. Structural cardiac remodeling with myocardial fibrosis is a hallmark of progression to heart failure. LMW-FGF-2 significantly attenuated TGF-beta1-induced myofibroblast-mediated ECM remodeling — the pathway is modifiable downstream of TGF-beta itself. PMC3072437
Blood pressure increases it.
Pressure is the load the muscle rebuilds against: hypertension causes hemodynamic overload and induces gradual structural remodeling — cardiomyocyte hypertrophy thickening the ventricular wall, plus interstitial and perivascular collagen deposition (PMC11219059). The consequence is a stiffer, less compliant ventricle: diastolic dysfunction first, and over time the transition from hypertrophy to heart failure (PMC8110048). Verbatim: “RAAS activation worsens LVH by increasing blood pressure and by directly affecting cardiac myocytes with AT-II and aldosterone”. doi 10.7759/cureus.26642 · PMC11219059
Cardiac scarring cells increases it.
10.1038/nrcardio.2017.57 — phase three — where a recoverable illness becomes a permanent one. 'profibrotic cytokines and mediators released during acute myocarditis in susceptible individuals activate fibroblasts and recruit new fibroblast differentiation via endothelial mesenchymal transition leading to cardiac remodeling and dilated cardiomyopathy' (Mayo/Elsevier chapter — Viral Myocarditis and Dilated Cardiomyopathy: Mechanisms of Cardiac Injury, Inflammation, and Fibrosis). Scar is not muscle. It does not contract, and once laid down it stays. This is the step that decides whether the heart recovers its function OR keeps a permanent deficit. doi 10.1038/nrcardio.2017.57
Mast cell enzyme increases it.
The enzyme the mast cell releases, and it remodels the heart. Mast cell tryptase rises in the inflamed heart alongside stem cell factor, and both are suppressed by agents that help (doi 10.1186/1476-9255-7-39 (pmc2922108) — Matsumori a, Yamamoto k, Shimada m. Cetirizine a histamine H1 receptor antagonist improves viral myocarditis, j Inflamm 2010). 'myocardial histamine and tryptase content, and mast cell density ARE higher in heart failure due to idiopathic dilated or ischemic cardiomyopathy than in control hearts'. ⇒ the cell that causes hay fever also helps turn an inflamed heart into a stiff one. doi 10.1186/1476-9255-7-39
What it drives
It increases Enlarged heart.
10.3390/v17040484 — phase three — where a recoverable illness becomes a permanent one. 'profibrotic cytokines and mediators released during acute myocarditis in susceptible individuals activate fibroblasts and recruit new fibroblast differentiation via endothelial mesenchymal transition leading to cardiac remodeling and dilated cardiomyopathy' (Mayo/Elsevier chapter — Viral Myocarditis and Dilated Cardiomyopathy: Mechanisms of Cardiac Injury, Inflammation, and Fibrosis). Scar is not muscle. It does not contract, and once laid down it stays. This is the step that decides whether the heart recovers its function OR keeps a permanent deficit. doi 10.3390/v17040484
Blends that modulate it
Each blend page names this pathway and carries the study behind its claim.
See it on the map
Open the causal map to follow this pathway upstream and downstream, arrow by arrow, each with its study.