Cardiac output is the product of heart rate by stroke volume. In a sense to a car engine, heart rate is the RPM and stroke volume is the power, and cardiac output is the speed. Therefore, you need both to estimate speed. Medication, hydration, and food can effect stroke volume. Crdiotoxicity, is defined as damage to the heart muscle, valve, or arrhythmia due to medication intake. The more medication an individual takes the greater the chance to Cardiotoxicity. The example below shows sixty minutes recordings of cardiac parameter from individual who take liver medication and beta blockers. The initial recordings indicated high blood pressure at normal heart rate as a clinician will observe at a check up. Since we performed recording for long duration, we are able to observe that blood pressure reach to the normal range after twenty minutes. However, stroke volume decrease to a very low range and therefore cardiac index (cardiac output over body surface area) is at critical zone where the subject feel dizzy and fatigue. As result, subject medication should be adjusted.
Subject is under multiple medication which reduce his heart contraction ability.