Bolus intravenous nitroglycerin predominantly reduces afterload in patients with excessive arterial elastance.
OBJECTIVE
We hypothesized that bolus intravenous nitroglycerin would be an afterload-reducing agent in patients with excessive initial afterload for their level of left ventricular systolic function. Conversely, bolus intravenous nitroglycerin should be a preload-reducing agent in patients without excessive initial afterload.


BACKGROUND
Although nitroglycerin has both preload- and afterload-reducing actions, methods to predict its predominant site of action in an individual patient have not been previously described.


METHODS
Left ventricular pressure-volume relations were recorded with micromanometer and conductance catheters during bolus injection of intravenous nitroglycerin in 27 patients with both normal left ventricular systolic function and varying degrees of congestive heart failure. Preload was determined by end-diastolic volume, afterload by effective arterial elastance, left ventricular systolic function by end-systolic elastance and coupling of afterload and ventricular function by the ratio of effective arterial elastance to end-systolic elastance (Ea/Ees ratio). An Ea/Ees ratio > 1 was defined as excessive afterload for the level of ventricular function.


RESULTS
Patients with an initial Ea/Ees ratio < 1 (Group 1) constituted a group of normotensive patients with intact ventricular function who exhibited a predominant reduction in preload in response to intravenous nitroglycerin. Those with an initial Ea/Ees ratio > 1 and normal or mildly depressed ventricular function (Group 2a) constituted a group of patients, most of whom were hypertensive, who exhibited a predominant afterload reduction. Finally, those with an initial Ea/Ees ratio > 1 and abnormal ventricular function (Group 2b) constituted a group of patients with clinical congestive heart failure who exhibited both preload and afterload reduction but a predominant afterload reduction because stroke volume increased.


CONCLUSIONS
Patients with normal arterial elastance and ventricular function respond to nitroglycerin with a predominant preload reduction, whereas patients with either excessive arterial elastance or abnormal ventricular function respond with a predominant afterload reduction.
Haber
H L
HL
Department of Internal Medicine, University of Virginia Health Sciences Center, Charlottesville 22908.
Simek
C L
CL
Bergin
J D
JD
Sadun
A
A
Gimple
L W
LW
Powers
E R
ER
Feldman
M D
MD
D000704:Analysis of Variance; D001794:Blood Pressure; D016022:Case-Control Studies; D005260:Female; D006333:Heart Failure / Q000503:physiopathology*; D006339:Heart Rate; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D005996:Nitroglycerin / Q000008:administration & dosage / Q000494:pharmacology*; D013318:Stroke Volume; D014655:Vascular Resistance / Q000187:drug effects*; D016277:Ventricular Function, Left / Q000187:drug effects*
D005996:Nitroglycerin