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Significant Physiologic and Hemodynamic Differences Between Adenosine with and without Low-level Treadmill Exercise in Patients Complaining of Dyspnea

Cooper Heart Institute, Robert Wood Johnson Medical School, Camden, NJ

PURPOSE: Adenosine with low-level treadmill exercise is preferred due to superior images and favorable side-effect profile. Surprisingly, little data exists on the hemodynamic effects of additional exercise on adenosine infusion in largely sedentary patients. First Pass Radionuclide Angiography (FPRNA) can simultaneously evaluate both ventricles, and pulmonary function at rest and at peak stress using well-validated non-invasive hemodynamic parameters. We used adenosine testing with and without exercise to evaluate consecutive patients presenting with dyspnea to determine the hemodynamic effects of the additional exercise.

METHODS: Adenosine was infused at 140 ug/kg/min for 6 minutes while sitting in a chair or walking on a treadmill (1.0 mph, 0% grade). Rest and stress FPRNA were obtained after 15-45 millicurie of sestamibi. Imaging was performed with Sim-400 multicrystal camera.

RESULTS: 60 patients (60% female) with mean age 66.2 years were evaluated. 33 patients (55%) exercised (+EX) and 27 patients did not (-EX). Baseline variables were similar in both groups except age, cardiac index, and pulmonary mean transit time (PMTT). Adenosine infusion clearly changes most of the parameters measured (Table 1
Table 1. Univariate comparison of hemodynamic parameters in patients with and without exercise

Hemodynamic Variable (Change from rest to exercise) Without Walk (N=27) With Walk (N=33) Test of Significance Cardiac output –mean (SD) 1.06 (0.39) 3.15 (0.35) t –4.01, df 58, P < 0.001 Cardiac index –mean (SD) 0.51 (0.20) 1.54 (0.17) t –3.92, df 58, P < 0.001 Time to peak flow –mean (SD) 0.74 (12.06) - 37.70 (11.87) t 2.25, df 58, P=0.03 Peak flow rate–mean (SD) 0.10 (0.09) 0.93 (0.18) t –3.82, df 58, P < 0.001 Pulmonary mean transit time –mean (SD) - 0.80 (0.42) - 1.27 (0.23) t 1.04, df 58, P=0.30

). Compared to -EX group, +EX patients had significant augmentation (rest compared to stress) in cardiac output (P< 0.001) and cardiac index (P< 0.001). The addition of exercise significantly improved diastolic function due to increased peak filling rate (P < 0.001) and shortened time to peak filling (P < 0.05) in the +EX group. These effects of exercise remained significant in multiple regression models (Table 2
Table 2. Multivariate comparison of hemodynamic parameters in patients with and without exercise

Dependent Variable (Change from rest to exercise) Exercise vs No Exercise Groups Variables Controlled Cardiac output P=0.002 Age,P= 0.06 Cardiac index P=0.03 Age, P= 0.06 Cardiac index at rest, P=0.001 Time to peak flow P=0.01 Age, P=0.18 Peak flow rate P=0.003 Age, P=0.07 pulmonary mean transit time P=0.004 Age, P=0.36 PMTT, P<0.001

) that controlled for significant baseline differences in age, cardiac index, and pulmonary mean transit time. When controlling for significant difference in PMTT between the groups at rest, the change in PMTT was significantly different between the groups.

CONCLUSION: Adenosine infusion alone has significant effects on non-invasive hemodynamic parameters measured by FPRNA. Additional low-level exercise results in improved images and significantly augments many functional parameters increasing the test’s utility.

CLINICAL IMPLICATIONS: FPRNA is becoming the favored test to assess cardiovascular function in patients with dyspnea. Adenosine infusion and exercise provide additive benefits.

DISCLOSURE: N. Tripathi, None.