Clinician sheet — Calf muscle pump

Physiology (established)

Upright venous return depends on veins, one-way valves, and muscle pumps. StatPearls lists calf-pump failure among CVI etiologies with reflux and obstruction. NBK430975

AVF: calf muscles acting as a pump propel venous blood toward the heart; inadequate valves or impaired pumping → stasis.

Mayo Clinic (varicose veins, 2024 page): “Muscles tighten in the lower legs to act as pumps.”

Mayo Clinic (DVT): when legs do not move, calf muscles do not contract; contractions help blood flow; prolonged sitting (travel, bed rest) increases DVT risk.

Duplex ultrasound is the usual first CVI test; air plethysmography can assess reflux, obstruction, and muscle-pump function when duplex is incomplete (StatPearls).

Observational — cite as association only

Ghorbanzadeh et al., Vasc Med, DOI 10.1177/1358863X241311254. Mayo APG database, 7760 limbs / 3733 patients (2015–2023). Reduced CPF (EF) trended with higher CEAP (p<0.001). Reduced CPF independently associated with C5/C6 (OR 1.84, CI 1.5–2.2) after age, sex, incompetence, obstruction. Mildly reduced EF 40–49% not associated with ulcers. Not a treatment trial; does not prove walking heals ulcers.
McBane et al., Mayo Clin Proc. 2024;99(6):902-912, PMID 38661596. n=5913 consecutive APG patients; median f/u 2.84 y; 431 deaths. Mortality HRs vs EF ≥50%: 40–49% 1.4 (1.0–2.0); 30–39% 1.6; 20–29% 1.7; 10–19% 2.4 (1.7–3.3). Valve incompetence not independently predictive; CEAP was. Authors suggest muscular physiology may matter. Residual confounding likely. Do not claim ambulation prevents death from this paper.

Public counseling used in this package

Generic mobility: walk; seated heel/toe pumps on long sits or travel >4 h (CDC; Mayo). No prescribed exercise “dose.”

CDC Travelers’ Health: aspirin is not recommended to prevent travel clots; anticoagulants only as the patient’s clinician directed.

Compression garment type/strength: clinician-directed (Mayo Press). Not specified publicly.

Chronic swelling differential includes CVI, heart failure, kidney disease, lymphedema (Mayo Press; StatPearls).

Emergency language kept in the public script

DVT symptoms → prompt evaluation. CDC: about half of DVT are asymptomatic.
PE symptoms (sudden dyspnea, pleuritic pain, hemoptysis, syncope) → 911. Don’t wait. Don’t drive yourself.
CDC: DVT does not cause MI/stroke; arterial thrombosis does. PE is the venous emergency.

Calf muscle pump (“second heart in the calf”)

Physiology (established)

Observational — cite as association only

Public counseling used in this package

Emergency language kept in the public script

Refused in the public package