Coronary resistance

Coronary resistance is the physical resistance in the coronary arteries. It is calculated as follows:

Rcor =

mean diastolic aortic pressure

minus

mean diastolic pressure in the left ventricle (mmHg)

divided by

the coronary blood flow (ml / min x 100g)

(Müller 1985)

Pathophysiology

The coronary resistance consists of 3 components:

• Proximal component

It is formed in the epicardial conduction vessels (Classen 2009) and depends on the lumen width of the epicardial coronary artery.

• Distal component

It depends on the resistance of the intramyocardial arterioles (Herold 2019) and is mainly locally metabolically regulated. The coronary blood flow can increase 4 to 5 times by dilatation of the intramyocardial resistance vessels (Classen 2009).

• Extravasal component

The extravasal component depends on the systolic vessel compression as a consequence of the intramyocardial pressure increase (Herold 2019).

Increased left ventricular pressure results in increased extravasation resistance. This resistance exists from the subendocardium to the subbepicardium as a transmural resistance gradient.

As a result, the coronary reserve in the subendocardium is exhausted earlier than in the subbicardium. This explains why myocardial ischemia always occurs first in the subendocardium (Classen 2009).

Increase in coronary resistance

An increase in coronary resistance can be caused by:

• vasal factors such as
  • Macroangiopathy (e.g. CHD)
  • Microangiopathy (small vessel disease)
  • Coronary spasms (can be triggered by cocaine, among other things)
  • Anomalies of the coronaries
  • arteriovenous fistulas
  • congenital myocardial bridges
• Arrhythmias
• arterial hypertension

(Herald 2019)

• Hypercapnia (Kretz 1989)
• Various drugs (such as Atenolol etc. [Schlegel 1980])

Reduction of coronary resistance

• Tachycardia (Lüderitz 1983)
• various drugs (such as calcium antagonists [Wappler 2006], nitrates [Rietbrock 1986]) etc.

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2. Herold G et al (2019) Internal Medicine. Herold Publisher 238 - 245
3. Kretz F J et al (1989) Anaesthesia - Intensive care - Emergency medicine. Springer Publishing House 167
4. Lüderitz B et al (1983) Handbook of Internal Medicine: Volume IX Heart and Circulation. Springer Publishing House 379
5. Müller F et al. (1985) Pocketbook of medical and clinical diagnostics. J F Bergmann Publishing House Munich 128
6. Rietbrock N et al. )1986) Nitrate therapy today: The importance of pharmacodynamics and pharmacokinetics for dosage, dosage and clinical efficacy. Friedrich Vieweg publishing house 11 -12
7. Schlegel B et al (1980) Negotiations of the German Society for Internal Medicine: 86th Congress of Wiesbaden Springer Verlag 594
8. Wappler F et al (2006) Anaesthesia and concomitant diseases: Perioperative management of the sick patient Georg. Thieme Publishing House 70