Nicotine and Nicotine Replacement Therapy Use During Myocardial Perfusion Imaging

These principles similarly apply to patients with underlying moderate-to-severe cardiovascular disease (CVD). With nicotine use at rest, patients with significant CAD do not experience as dramatic of an increase in coronary blood flow, which typically decreases or remains the same despite increased myocardial work.¹⁰ This may be because patients with moderate-to-severe CAD often have flow-limiting stenoses and damaged endothelium that do not allow vessels to respond as efficiently to increased myocardial demand or to nicotine’s β-receptor–mediated vasodilatory effects.^10,11 Moreover, when stressed, diseased coronary arteries are not able to further dilate and nicotine’s α-receptor–mediated vasoconstriction effects dominate.^10,11

In a study by Quillen and colleagues of patients with moderate-to-severe CAD, the mean diameter of proximal coronary artery segments decreased by 5%, the distal coronary diameter decreased 8%, and the coronary vascular resistance increased by 21% while smoking at rest.¹² The investigators did not analyze how parameters changed when these diseased coronary arteries were stressed using a medication during MPI. However, it can be predicted that coronary arteries would have constricted to a similar or greater degree than observed in Czerin and colleagues’ study, given that the underlying myocardium was diseased and more susceptible to nicotine’s vasoconstriction effects.⁹ Importantly, these studies have several limitations, most notably that they are older and have small sample sizes. Additionally, while statistically significant differences were found in the degree of changes in coronary circulation with nicotine use at rest and during stress, it is unclear whether this translates to a clinically significant and impactful finding.^9-12

Nicotine Replacement Therapy and Stress Testing

Given the association between cigarette smoking and CAD, medical practitioners strongly encourage patients to quit smoking to reduce their risk of adverse cardiovascular outcomes. Various smoking cessation treatments are available for patients. Common, readily accessible forms of therapy include nicotine replacement products (Table 2).

Early studies of NRT in patients with underlying CVD found an increased risk of cardiovascular events, such as myocardial infarction, presumably due to the nicotine content of these products.^13,14 However, the concentration of nicotine in NRT is substantially lower than that found in cigarettes and in some formulations, such as transdermal patches, nicotine is delivered over a prolonged period of time.¹⁵ For this reason, NRT is thought to be safe in patients with underlying CVD and stable ischemic heart disease. A recent systematic review and meta-analysis found that while NRT may be associated with tachycardia, it did not increase the risk of more serious cardiovascular adverse effects (AEs).^16,17

Given the lower nicotine concentration in NRT products, the associated hemodynamic effect of nicotine also is thought to be less pronounced. In a study conducted by Tzivoni and colleagues in patients with CAD using transdermal nicotine patches, no differences in blood pressure, heart rate, ischemia, or arrhythmias were found from baseline to 2 weeks.¹⁸ These findings were further confirmed in a small study by Lucini and colleagues, which found that nicotine patches produced slight hemodynamic effects, but to a lesser extent than cigarette smoking.¹⁹ For the NRT gum formulation, while a small study found that 4 mg produced coronary vasoconstriction in patients with underlying CAD, a study by Nitenberg and Antony demonstrated that healthy and diseased coronary arteries did not significantly constrict while patients were using nicotine gum both before and after a cold pressor test, suggesting a lesser degree of coronary vasoconstriction than nicotine from cigarette smoking.^20,21 Similar findings have been described with the nicotine intranasal spray in a study by Keeley and colleagues, which showed no additional AEs on myocardial demand or vasoconstriction when an intranasal nicotine spray was added to cigarette smoking.²² Importantly, a review of the transdermal and gum formulations found that these less pronounced hemodynamic effects were observed across different doses of NRT; however, further studies are needed to clarify the relationship between NRT dose and cardiovascular effects.²³

Overall, NRT does not seem to activate the SNS to the same degree as nicotine obtained via cigarette smoking and likely does not increase the myocardial oxygen demand as much. Additionally, by containing a lower concentration of nicotine, NRT may not impair the myocardium’s ability to supply oxygen to coronary arteries to the same extent as nicotine from cigarette smoking. Therefore, the effects of NRT on MPI using a stress-inducing medication may not be as pronounced. However, due to study limitations, results should be interpreted cautiously.^18-23

Conclusions

Because of the close relationship between cigarette smoking and CAD, many patients with underlying CVD are either current smokers or may be using NRT for smoking cessation. Therefore, the question of whether to refrain from nicotine use prior to MPI is clinically relevant. Currently, there is a lack of high-quality studies demonstrating the effects of nicotine and NRT on coronary perfusion. Because of this, the impact of nicotine and NRT use on the accuracy of MPI using stress-inducing medications remains uncertain. Nevertheless, given that nicotine and NRT may largely affect the accuracy of imaging results, several institutions have adopted protocols that prohibit patients from using these drugs on the day of nuclear stress testing.

There are currently no data specifying the number of hours to hold nicotine products prior to cardiac stress testing. It is generally recommended that other medications that affect coronary blood flow be held for 5 half-lives before conducting MPI.⁴ Following the same guidance for nicotine and NRT may present a reasonable approach to ensure accurate imaging results. Based on the discussed literature, patients should be instructed to refrain from cigarette smoking for at least 5 to 10 hours prior to MPI, given nicotine’s half-life of about 1 to 2 hours.²⁴

The data for NRT are less clear. While use of NRT may not be an absolute contraindication to conducting MPI, it is important to consider that this may affect the accuracy of results. Given this uncertainty, it is likely ideal to hold NRT prior to MPI, based on the specific formulation of NRT and that product's half-life. Further robust studies are needed to analyze the impact of nicotine and NRT on the accuracy of nuclear stress testing using a medication.