Viagra (sildenafil) has been released to the Canadian market. Other similar
medications are forthcoming This will have a significant impact on our
practises. We all can expect to see many patients who will ask for the
medication or who wish to be informed of the safety and suitability of
this agent in their case. Many patients with erectile dysfunction have
manifest or occult coronary artery disease. In this context it is important
that we are all well versed in the cardiovascular implications of Viagra.
Erectile dysfunction (ED) - Clinical context:
- ED is common-52% of men age 40-70 (10% complete;25% moderate;17% minimal)
- ED is a marker of underlying organic disease:
- Atherosclerosis (CAD,PVD), hypertension, diabetes, renal failure,
- Hyper or hypothyroidism, hypogonadism, hyperprolactinemia
- Alzheimers disease, multiple sclerosis
- Spinal injury, autonomic dysfunction
- Post urologic surgery
- Medications may be implicated in ED:
- Anti-hypertensives, anti-depressants, hormones, tranquillisers
- Alcohol, smoking, diet
Sexual activity and the cardiac patient:
- Energy expenditure of intercourse (3-4 METS)
- Energy expenditure of ejaculation and intercourse (4-5 METS)
- Equivalent activities1:
- Walking 3 mph, level = 3-3.5 METS
- Bruce protocol - stage I = 5 METS
- Golf, pulling cart = 3-4 METS/carrying clubs = 4-5 METS
- Bruce protocol - stage II = 7 METS
- Walking upstairs = 4-7 METS
- Cycling 12 mph, level = 7-8 METS
- Swimming- front crawl = 9-10 METS
- Risk of repeat MI triggered by sexual activity in MI survivors2:
- Low risk male ( non-smoker, non-diabetic, 50 years old) 1.01/million/hour
- Clinically high risk male 1.2 /million/hour
- Risk decreases with regular physical activity > 6 METS
- 0-1/wk RR 3.0
- 2x/wk RR 1.9
- > 3x/wk RR 1.2
Patients in Whom Sexual Activity May Carry Significant Cardiovascular
Sexual activity carries a small but defined CV risk, even in asymptomatic
patients, however patients with the following conditions should not receive
any therapy for ED until the CV condition has been clarified and stabilized.
- Patients with recent acute cardiac ischaemic syndromes ( six weeks)
- Patients with angina or ischaemia at low levels of exercise(unable
to complete stage I of Bruce protocol or climb 2 flights of stairs;
approximately 4-5 METS)
- Patients with poorly controlled, severe HPT ( SBP > 180 or DBP
> 115 mm Hg)
- Patients with recent Cerebrovascular event ( less than 6 weeks)
- Patients with any medical or surgical condition that may be aggravated
by sudden increases in BP
- Inactive patients with CV disease or significant risk factors who
are presently sexually inactive and in whom functional activity has
not been determined.
Which Patients Require Cardiac Evaluation Prior to Starting Viagra?
- All patients with Class III dyspnea or angina
- Post MI or post unstable angina
- Patients receiving complicated multi-drug anti-hypertensive therapy
- Patients with significant aortic stenosis
Patients to Whom Viagra (sildenafil) should be Prescribed with Caution:
- Patients with active coronary ischaemia and are not on nitrates
- Patients with CHF and borderline low BP or borderline low volume status
- Patients with severe renal or hepatic dysfunction (lower sildenafil
- Patients on drugs that can prolong the half life of Viagra (erythromycin,
- Patients with retinitis pigmentosa
Nitrate / Viagra Interaction:
- Viagra is a potent inhibitor of cGMP-specific phosphodiesterase type
- Viagra enhances the relaxant effect of endogenous NO (bitric oxide)
on the corpus cavernosum
- Systemic effects: a balanced modest vasodilator/ anti-spasmodic which
will enhance the vascular actions of endogenous NO (nitric oxide). Similar
to a weak nitrate. No direct cardiac effects.
- Potentiates the hypotensive effects of exogenous nitrates resulting
in severe hypotensive response.
- Administration to patients who are currently using organic nitrates
in any form is contra-indicated.
- This includes; Sublingual NTG tablets or spray, oral long acting nitroglycerin
preparations, isosorbide mononitrate, isosorbide dinitrate, sodium nitroprusside
and amyl nitrate (poppers)
Nitrates in any form are contra-indicated for 24 hours after Viagra
administration. Patients should alert ambulance attendants and ER staff
that they have Viagra on board should chest pain or ischaemia develop
during its use. Anti-ischaemic measures should avoid nitrate administration.
1. Pashkow and Dafoe, Eds. Clinical Cardiac
Rehabilitation, Appendix A. 1999.
2. Muller JE et al. JAMA. 1996;275:1405-1409.
Reference: ACC/AHA Expert Consensus Document; Use of Sildenafil
(Viagra) in Patients With Cardiovascular Disease. Circulation. 1999;99:168-177.