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Under most circumstances, the body attempts to maintain a steady mean arterial pressure. [2] When there is a major and immediate decrease (such as that due to hemorrhage or standing up), the body can increase the following: Heart rate; Total peripheral resistance (primarily due to vasoconstriction of arteries) Inotropic state
Chronotropic effects (from chrono-, meaning time, and tropos, "a turn") are those that change the heart rate. Chronotropic drugs may change the heart rate and rhythm by affecting the electrical conduction system of the heart and the nerves that influence it , such as by changing the rhythm produced by the sinoatrial node .
Non-dihydropyridine calcium channel blockers such as verapamil block the slow inward calcium current in cardiac tissues, thereby having a negatively dromotropic, chronotropic and inotropic effect. [5] This (and other) pharmacological effect makes these drugs useful in the treatment of angina pectoris.
Drugs that positively render the effects of catecholamines such as norepinephrine and epinephrine that enhance contractility are considered to have a positive inotropic effect. The ancient herbal remedy digitalis appears to have both inotropic and chronotropic properties that have been recorded encyclopedically for centuries and it remains ...
Negative inotropic agents decrease myocardial contractility and are used to decrease cardiac workload in conditions such as angina. While negative inotropism may precipitate or exacerbate heart failure in the short term, certain beta blockers (e.g. carvedilol , bisoprolol and metoprolol ) have been believed to reduce long-term morbidity and ...
A plot of a system's pressure versus volume has long been used to measure the work done by the system and its efficiency. This analysis can be applied to heat engines and pumps, including the heart. A considerable amount of information on cardiac performance can be determined from the pressure vs. volume plot (pressure–volume diagram).
The effect of these compounds on the cardiovascular system presents a reason for concern, as they can directly affect the function of the heart through their inotropic and chronotropic effects. In terms of inotropic activity, excessive cardiac glycoside dosage results in cardiac contractions with greater force, as further calcium is released ...
Isoprenaline has positive inotropic and chronotropic effects on the heart. β 2-Adrenergic receptor stimulation in arteriolar smooth muscle induces vasodilation. Its inotropic and chronotropic effects elevate systolic blood pressure, while its vasodilatory effects tend to lower diastolic blood pressure.