When cardiac output and total peripheral resistance (TPR) remain constant, a decrease in arterial compliance leads to an increase in pulse pressure. This relationship can be seen in Figure 17.16. Additionally, diminished arterial compliance increases the workload on the left ventricle, even if stroke volume, TPR, and mean arterial pressure (Pa) are equal between individuals.

If heart rate and stroke volume remain constant, an increase in TPR causes an increase in Pa.

When arterial compliance remains constant, an increase in TPR results in proportional increases in systolic and diastolic pressure, keeping the pulse pressure unchanged (Figure 17.17A). However, arterial compliance is not linear. As Pa increases and the artery is stressed, compliance decreases (Figure 17.17B). Therefore, pulse pressure increases when Pa is elevated.

The impact of arterial compliance on myocardial energy consumption is shown in Figure 17.18. In this experiment, the cardiac output from the left ventricle either flowed through the natural route (the aorta) or was directed through a stiff plastic tube to the peripheral arteries. Despite similar TPR values, the data demonstrated that myocardial oxygen consumption was significantly higher when blood flowed through the less compliant plastic tubing compared to the more compliant aorta. This indicates that the left ventricle expends more energy to pump blood through a less compliant conduit.
Eq. 19.1 ), also affects pulse pressure. This relationship is illustrated in
Fig. 17.16 . When cardiac output and TPR are constant, a decrease in arterial compliance results in an increase in pulse pressure. Diminished arterial compliance also imposes a greater workload on the left ventricle (i.e., increased afterload), even if stroke volume, TPR, and Pa are equal in the two individuals.
As previously discussed, if the heart rate and stroke volume remain constant, an increase in TPR causes Pa to increase.
•Fig. 17.15 Effect of a Change in Stroke Volume on Pulse Pressure in a System in Which Arterial Compliance Remains Constant Over the Prevailing Range of Pressures and Volumes. Alargerincrementinbloodvolume,whereby(V4− V3)> (V2− V1),resultsingreatermeanbloodpressure(PB > PA)andagreaterpulsepressure,sothat(P4− P3)> (P2− P1).
When arterial compliance is constant, an increase in TPR leads to proportional increases in systolic and diastolic pressure so that the pulse pressure is unchanged (Fig. 17.17A ). However, arterial compliance is not linear. As Pa increases and the artery is stressed, compliance decreases (see
Fig.
17.17B ). Because of the decrease in arterial compliance with increased Pa, pulse pressure increases when Pa is elevated.
Effect of Arterial Compliance on Myocardial Energy Consumption
The increased cardiac energy requirement imposed by a rigid arterial system is illustrated in
Fig. 17.18 . In the data depicted in
Fig. 17.18 , the cardiac output from the left ventricle either was allowed to flow through the natural route (the aorta) or was directed through a stiff plastic tube to the peripheral arteries. In this experiment, the TPR values were virtually identical, regardless of which pathway •Fig. 17.16 Foragivenvolumeincrement(V2− V1),reducedarterialcompliance(complianceB[LowCa]< complianceA[HighCa])resultsinincreasedpulsepressure,whereby(P4− P1)> (P3− P2).Pa,meanarterialpressure.
•Fig. 17.17 Comparisonoftheeffectsofagivenchangeinperipheralresistanceonpulsepressure(P)whenthepressure-volumecurveforthearterialsystemiseitherrectilinear(A) orcurvilinear(B). Theincrementinarterialvolumeisthesameforbothconditions;thatis,(V4−V3)=(V2−V1).PressureABVolumeP1V1V2V3V4P3P6P4P2–P5–PressureP1V1V2V3V4P3P6P4P2–P5– •Fig. 17.18 Therelationshipbetweenmyocardialoxygencon-sumption(1mL/100g/beat)andstrokevolume(inmilliliters)inananesthetizeddogwhosecardiacoutputcouldbepumpedbytheleftventricleeitherthroughtheaortaorthroughastiffplastictubetotheperipheralarteries.(ModifiedfromKellyRP,TuninR,KassDA.Circ Res. 1992;71:490.)Plastic tubing Native aorta Stroke volume (mL) 5 0 0.05 O 2 consumption (mL) O2/100 g/beat)0.1 10 15 was selected. The results showed that for any given stroke volume, myocardial oxygen consumption was substantially greater when the blood was diverted through the plastic tubing than when it flowed through the aorta. The increased oxygen consumption indicates that the left ventricle has to expend significantly more energy to pump blood through a less compliant conduit than through a more compliant conduit.