Place · Level 3
Cardiovascular System
心脏泵、血管内皮、脂蛋白交通、斑块演化和血压调控共同决定循环质量
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Chapter 1
The pump
The pump
The heart needs adenosine triphosphate: The cell's universal energy currency — almost everything that costs energy spends it., electrolytes, and oxygen. K⁺/Na⁺/Mg²⁺/Ca²⁺ run excitation-contraction coupling; iron delivers oxygen.
By the numbers
The heart never rests for a lifetime; the numbers reveal its dependence on nutrition:Beat rate: 60–80 beats/min at rest, ~100,000 beats/day, ~3 billion beats over a lifetimePump output: 5 L/min at rest, 25 L/min in exercise, ~7000 L/dayOxygen consumption: ~5% of resting cardiac output at rest, i.e. 10–15% of whole-body resting oxygen consumption — per unit weight, higher than the brainEnergy source: healthy myocardium gets ~60–70% of its adenosine triphosphate: The cell's universal energy currency — almost everything that costs energy spends it. from fatty acid β-oxidation, 20–30% from glucose, 5–10% from lactate and ketones; the heart is the organ that most prefers fatCoronary blood flow: ~70 ml/min per 100g of myocardium at rest — less than half of the kidney but 5× resting skeletal muscle
One key vulnerability: coronary arteries only perfuse during cardiac diastole, because systole compresses the vessels. So sustained tachycardia (> 150) or too-short diastole (severe hypertension plus aortic stenosis) leaves the myocardium itself hypoxic — that's the mechanical root of 'rapid heart rate as a cardiovascular risk in itself'.
So β-blockers lowering heart rate isn't just 'making the heart comfortable' — it's also giving the myocardium time to receive its own oxygen supply.
Chapter 2
Endothelium
Endothelium
Endothelium senses shear stress and releases nitric oxide to dilate vessels. Aerobic exercise repeatedly trains this system.
Nitric oxide
Nitric oxide (nitric oxide: A small signal molecule from the vessel lining that relaxes the vessel-wall muscle so the vessel widens.) was the first gas signaling molecule discovered (Furchgott / Ignarro / Murad, 1998 Nobel Prize).Synthesis: L-arginine + O₂ → NO + L-citrulline, catalyzed by eNOS (endothelial nitric oxide synthase), requiring BH4 (tetrahydrobiopterin) and NADPH cofactors.
Three main triggers: blood flow shear stress, which rises sharply during exercise — the core mechanism for aerobic training improving vessels; acetylcholine; bradykinin (part of how ACE inhibitor antihypertensives work).
Downstream effects: NO enters vascular smooth muscle and activates guanylate cyclase to produce cGMP, relaxing smooth muscle and dilating vessels; it also inhibits platelet aggregation and leukocyte adhesion (anti-atherosclerotic).
Factors that raise NO: regular aerobic plus resistance training; leafy greens and beets contain nitrates that oral bacteria reduce to nitrite, which then forms NO independently of the eNOS pathway — beetroot juice can briefly lower BP 3–5 mmHg; adequate sleep; not smoking.
Factors that lower NO: chronic hyperglycemia plus insulin resistance; mouthwash killing oral bacteria blocks the nitrate → nitrite pathway; sedentary lifestyle.
'Endothelial dysfunction' is when NO production is insufficient or rapidly broken down — the earliest, also reversible, step in atherosclerosis, well before LDL elevation, plaques, and symptoms.
Chapter 3
Plaque cascade
Plaque cascade
Atherosclerosis is not 'fat clogging a pipe'. It is a decades-long chronic inflammatory cascade. Understanding the steps reveals exactly where each intervention (diet, statin, exercise, quitting smoking) works.
Six steps over decades
Step 1 — endothelial injury (begins as early as age 10–20)Chronic hypertension, hyperglycemia, smoking, and oxidative stress reduce endothelial nitric oxide: A small signal molecule from the vessel lining that relaxes the vessel-wall muscle so the vessel widens. and raise permeability. Asymptomatic, but the vessel is already 'scratched'.
Step 2 — LDL infiltration + oxidation
Small dense LDL particles (sdLDL) pass through the damaged endothelium and are oxidized under the intima → ox-LDL. This is the real antigen the immune system treats as a 'foreign threat'.
Step 3 — macrophage phagocytosis → foam cells
Monocytes are recruited beneath the endothelium, differentiate into macrophages, and engulf ox-LDL via scavenger receptors (CD36, SR-A) in large quantities — this pathway has no negative feedback; macrophages bloat into foam cells and die.
Step 4 — fatty streak
Foam cells plus extracellular lipid accumulate into visible yellow streaks. Already present in childhood. This step is still reversible — restoring endothelium and reducing LDL inflow can resolve it.
Step 5 — fibrous plaque + calcification
Smooth muscle cells migrate into the intima, secreting collagen to form a fibrous cap over the lipid core. Calcium starts depositing. The plaque begins to narrow the vessel — angina, intermittent claudication appear.
Step 6 — plaque rupture → acute thrombus
The critical inflection point: not 'vessel fully blocked' but the fibrous cap suddenly ruptures, exposing the lipid core → platelets aggregate instantly + coagulation activates → acute thrombus → full occlusion → MI / ischemic stroke.
Rupture triggers are often inflammation + sharp shear-stress spikes (morning waking, severe emotional stimulation) — which is why MIs cluster between 6 and 10 am (Muller 1985).
Where interventions land
Knowing exactly which step each intervention blocks is what reveals why some things matter and others matter less:Quit smoking → Step 1 (endothelial protection) — one year after quitting, cardiovascular risk is halved; the cheapest single intervention with the largest effectLower LDL (statin, diet, exercise) → Step 2 (less LDL into the vessel wall) — statins lower LDL 30–50%, cutting MI 25–35%Lower blood pressure → Step 1 + Step 6 (reduced shear stress + reduced rupture risk) — each 10 mmHg drop in SBP cuts stroke 27%Omega-3 EPA/DHA → Step 5 + Step 6 (plaque stabilization, anti-inflammatory, antiarrhythmic)Exercise → Step 1 (improved endothelial nitric oxide: A small signal molecule from the vessel lining that relaxes the vessel-wall muscle so the vessel widens.) + systemic metabolism + anti-inflammatoryAspirin (low-dose) → Step 6 (inhibits platelet aggregation) — secondary prevention (existing MI / stroke / PAD) almost universally recommended; primary prevention USPSTF 2022 withdrew the 60+ recommendation (bleeding risk exceeds benefit); 40–59 needs individualized decision + physician evaluation; < 40 not recommendedGlucose control → Step 1 (lower AGEs + reduced inflammation)
Don't underestimate:
Periodontitis / chronic infection → Step 1, systemic inflammation drives endothelial damage; gum health correlates with cardiovascular eventsSleep < 6 h → worsens multiple steps (BP, inflammation, insulin resistance, autonomic imbalance)
Don't overestimate:
Solo 'ω-3 supplementation' has weak evidence for primary prevention; high-dose (3–4 g) helps when treating high TGMega-dose antioxidant supplements (vitamin E, β-carotene) are useless or harmful (HOPE, ATBC trials) — they can't precisely block the key ox-LDL step and end up disrupting other redox signaling
Chapter 4
Lipoprotein traffic
Lipoprotein traffic
Dietary fat type influences low-density lipoprotein cholesterol: The so-called 'bad cholesterol' — the higher it is, the more plaque tends to build in artery walls.; trans is worst, saturated depends on what replaces it, omega-3 modulates TG and inflammation.
ApoB family
'Is your cholesterol high?' is an over-simplified question. What actually predicts cardiovascular events is apolipoprotein B: One sits on every artery-clogging particle, so counting it counts the harmful particles directly. particle count + lipoprotein(a): A largely gene-set lipoprotein particle that independently raises cardiovascular risk., not total cholesterol:Atherogenic lipoproteins (containing ApoB-100):
LDL — the lead character, enters the vessel wall, gets oxidized, triggers plaqueVLDL / IDL — LDL precursors, triglyceride-richLp(a) — a special particle made of LDL plus an apo(a) tail, determined by the LPA gene (90% genetic + almost unaffected by diet / statin); ~20% of Asians are elevated → early coronary heart disease risk 2–3×
Protective lipoproteins (containing ApoA-I):
HDL — reverse cholesterol transport, but 'higher HDL is better' is wrong — hereditary very high HDL is actually associated with higher risk (Voight 2012 Mendelian randomization)
The modern way to look at this:
low-density lipoprotein cholesterol: The so-called 'bad cholesterol' — the higher it is, the more plaque tends to build in artery walls. — entry-level metric, < 3.4 mmol/L (~ 130 mg/dL) is a rough target for healthy peopleApoB — more accurate, < 80 mg/dL low-risk, high-risk target < 60Lp(a) — test once in a lifetime is enough (essentially unchanging), but many people have never tested. > 50 mg/dL (~ 125 nmol/L) suggests early interventionTriglyceride / HDL ratio — more sensitive marker for metabolic syndrome
Actual magnitude of dietary intervention (without medication baseline):
Reduce trans fat → LDL-C ↓ 5–15%Reduce saturated fat (replaced by PUFA) → LDL-C ↓ 5–10%Soluble fiber (β-glucan oats) + plant sterols → LDL-C ↓ 5–10%EPA/DHA (high-dose 3–4 g) → TG ↓ 20–30%, LDL-C unchanged or slightly up
Statins lower LDL 30–50%, reducing cardiovascular events ~25–35% (primary prevention) — this is the portion that nutritional intervention cannot equivalently replace.
Chapter 5
Blood pressure
Blood pressure
Blood pressure is set by kidney sodium-water balance, potassium, vessels, weight, sleep, stress, and movement.
DASH ranking
DASH (Dietary Approaches to Stop Hypertension) is the landmark NIH-led RCT from 1997, still the gold standard for BP-lowering diet today.The core differences from a typical American diet: fruits and vegetables doubled (8–10 servings/day); whole grains, low-fat dairy, legumes, nuts notably increased; red meat, sugary foods, and sodium notably decreased; potassium target raised to 4.7 g/day (typical diet ~2 g).
BP reduction magnitude (within 4 weeks): hypertensives' SBP drops 11.4 mmHg / vitamin D-binding protein: The blood transport protein that carries vitamin D to organs. drops 5.5 mmHg; normotensives' SBP drops 3.5 / DBP drops 2.1; layering on sodium reduction (< 2.3 g Na/day) drops SBP a further ~3 mmHg.
What magnitude is this? A single antihypertensive drug typically lowers BP 8–15 mmHg. DASH plus sodium reduction is equivalent to a full antihypertensive — the most certain and largest-magnitude evidence in nutritional intervention.
Lifestyle BP-lowering ranking (estimated magnitude, hypertensives):
1. Weight loss (-1 mmHg / -1 kg, in the BMI > 25 range)
2. DASH diet (-11 mmHg)
3. Sodium reduction (-4 to -6 mmHg)
4. Regular aerobic exercise (150 min/week, -5 to -8 mmHg)
5. Limiting / quitting alcohol (-3 mmHg)
6. Increasing potassium (-4 to -5 mmHg)
Stacking effects: doing all six together typically drops SBP 15–25 mmHg — enough that a substantial portion of early hypertension can temporarily not need medication. This isn't a miracle, it's RCT-confirmed numbers.
Chapter 6
Pattern over single nutrient
Pattern over single nutrient
Cardiovascular health is pattern-level: fiber, potassium, less trans fat, sodium control, movement, sleep, and medical care when needed.
Mediterranean RCT
PREDIMED (2013 NEJM, 7,447 people in Spain, 4.8-year median follow-up) is one of the strongest RCTs in cardiovascular nutrition.Three arms compared: Mediterranean diet plus extra-virgin olive oil (50 ml/day); Mediterranean diet plus mixed nuts (30 g/day); control on low-fat diet.
Results (primary endpoint = MI, stroke, cardiovascular death): the olive oil arm cut risk 30%; the nuts arm 28%; the stroke subgroup dropped 39–46% — stroke reduction even stronger than MI reduction.
Core recipe has several common points: large amounts of fruits, vegetables, whole grains, legumes, fish; olive oil as the main cooking fat; moderate red wine (1 cup at meals/day, not recommended to start for non-drinkers); red meat, processed meat, sugary foods kept minimal; no need to deliberately go low-fat — total fat can be 40% of energy, but types dominated by MUFA and PUFA.
Compared to a Western low-fat diet: Mediterranean isn't low-fat, it's 'good fat'. This is one of nutrition science's most important cognitive pivots in the past 20 years, shifting from 'eat less fat' to 'eat the right fat'.
Translating to common substitutions for Chinese cuisine: olive oil can be replaced with camellia or canola oil (low saturated); sardines and anchovies can be swapped for sea bass, salmon, mackerel; chickpeas and lentils for black beans, soybeans, red beans; red wine isn't recommended to promote actively — Chinese baseline drinking patterns carry high risk, and non-drinkers shouldn't start for health reasons.