[Hartnell GG, Wakeley CJ, Tottle A, Papouchado M, Wilde RP Limitations of
chest radiography in discriminating between aortic dissection and myocardial
infarction: implications for thrombolysis. J Thorac Imaging 1993
Spring;8(2):152-5.]  Abstract:  <TIMIa.TXT>

It has been stated that chest radiographic features of aortic dissection are a
contraindication to intravenous thrombolysis in patients with suspected acute
myocardial infarction. Excluding aortic dissection could significantly delay
such treatment in patients who would benefit from thrombolysis. Initial chest
radiographs of 18 patients with acute aortic dissection and 25 patients with
acute myocardial infarction were evaluated. The radiographs were studied by
two experienced radiologists for signs of aortic dissection. No radiographic
signs or combinations of signs accurately distinguished aortic dissection from
myocardial infarction. Patients with chest radiographic signs suggesting
aortic dissection but with clinical features suggesting myocardial infarction
should not be denied the benefits of immediate intravenous thrombolysis.

[Nicolini. FA, et al. Concurrent nitroglycerin therapy impairs tissue-type
plasminogen activator-induced thrombolysis in patients with acute myocardial
infarction. Am J Cardiol 1994;74(7):662.]
BACKGROUND:  Previous animal studies have indicated that concomitant
administration of nitroglycerin and tissue-type plasminogen activator (t-PA)
decreased the thrombolytic potential of t-PA.
METHODS:  This study, which was conducted in Italy but co-authored by
individuals from the University of Florida and the Cleveland Clinic
Foundation, examined the effect of nitroglycerin administration in patients
with acute myocardial infarctions (AMIs) who were treated with t-PA.  In
addition to t-PA infusions (100mg given over three hours), 47 patients were
treated with either IV nitroglycerin infusions (mean dose, 43mcg/min) or
saline beginning with initiation of thrombolytic therapy and continuing for
nine hours.
RESULTS:  When compared with control patients, those treated with
nitroglycerin exhibited significantly lower mean plasma t-PA antigen
concentrations.  EKG and enzymatic evidence of early reperfusion was noted in
10/11 controls (91%) and 26/36 patients receiving nitroglycerin (72%).  Ten of
these latter 26 (but no control patient) manifested subsequent evidence of
intermittent or sustained reocclusion.  Thus, ongoing reperfusion was
sustained in 91% of controls but in only 44% of patients receiving t-PA plus
nitroglycerin.  Control patients manifested a greater reduction in ST
elevation than patients receiving nitroglycerin, and a shorter time to CK
release.
CONCLUSIONS:  The authors suggest that concomitant administration of IV
nitroglycerin with t-PA may impair thrombolysis in patients with AMIs,
possibly due to augmentation of hepatic blood flow with resultant facilitation
of t-PA degradation.  17 references

[Romeo F, et al. Concurrent nitroglycerin administration reduces the
efficacy of recombinant tissue-type plasminogen activator in patients with
acute anterior wall myocardial infarction. Am Heart J 1995; 130(4):692.]

BACKGROUND:  Although patients being treated with recombinant tissue-type
plasminogen activator (rTPA) for acute myocardial infarction (AMI) often
receive concomitant IV nitroglycerin, a previous animal study has suggested
that nitroglycerin may adversely affect the thrombolytic potential of rTPA.
METHODS: This randomized, nonblinded, Italian study examined the impact of
adding IV nitroglycerin to rTPA on a variety of markers of efficacy in 60
patients with a first anterior AMI treated within four hours of the onset of
symptoms.  All patients got heparin and aspirin, as well as rTPA (100mg given
over three hours), while 27 patients also received concurrent IV nitroglycerin
(100mcg/min given over eight hours).
RESULTS:  On the basis of indirect EKG markers (angiograms were not routinely
done), patients treated with IV nitroglycerin plus rTPA were felt to be
significantly less likely than those treated with rTPA alone to reperfuse (56%
vs. 76%, p<0.05), and more likely to reocclude (53% vs. 24%, p<0.05).  Mean
time to presumed reperfusion was longer in the nitroglycerin group, and
patients receiving IV nitroglycerin had larger infarcts based on analysis of
cardiac enzymes and more frequent development of nonfatal ventricular
fibrillation (3/27 vs. 0/33), sustained ventricular tachycardia (10/27 vs.
5/33), pulmonary edema (4/27 vs. 1/33), or congestive heart failure (3/27 vs.
1/33).  Plasma TPA antigen levels in patients receiving concomitant IV
nitroglycerin were lower than those noted in patients receiving TPA alone.
CONCLUSIONS:  Preliminary findings in this small group of patients sugggest a
possible adverse effect of IV nitroglycerin on the actions of rTPA, perhaps
due to promotion of rTPA catabolism by nitroglycerin. 24 references