Comparison of efficacy and safety of intracoronary sodium nitroprusside and intravenous adenosine for assessing fractional flow reserve

OBJECTIVES

The purpose of this study was to compare the efficacy and safety of intracoronary (IC) nitroprusside and intravenous adenosine (IVA) for assessing fractional flow reserve (FFR).

BACKGROUND

IV infusion of adenosine is a standard method to achieve a coronary hyperemia for FFR measurement. However, adenosine is expensive, causes multiple side effects, and is contraindicated in patients with reactive airway disease. Sodium nitroprusside (NTP) is a strong coronary vasodilator but its efficacy and safety for assessing FFR is not well established.

METHODS

We compared FFR response and side effects profile of IC NTP and IVA. Bolus of NTP at a dose of 100 μg and IVA (140 μg/kg/min) were used to achieve coronary hyperemia.

RESULTS

We evaluated 75 lesions in 53 patients (60% male) mean age 61.6 ± 13.9 years. Mean FFR after NTP was similar to FFR after adenosine (0.836 ± 0.107 vs. 0.856 ± 0.106; P = 0.26; r = 0.91, P < 0.001). NTP induced maximal stable hyperemia within 10 sec (mean: 6.4 ± 1) which lasted consistently between 38 and 60 sec (mean 51 ± 7.5). NTP caused significant (14%), but asymptomatic decrease in mean blood pressure which returned to baseline within 60 sec. Adenosine caused shortness of breath in 26%, headache and flushing in 19%, and transient second degree heart block in 6% of patients. No adverse symptoms were reported after NTP.

CONCLUSIONS

IC NTP is as effective as IVA for measuring FFR. NTP is better tolerated by patients. Since NTP is inexpensive, readily available, well tolerated, and safe, it may be a better choice for FFR assessment.

Fractional flow reserve (FFR): changing the practice of interventional cardiology

Fractional flow reserve (FFR) has become an extremely valuable tool for assessing the hemodynamic significance of intermediate coronary lesions. This manuscript delineates the current guidelines regarding the use of FFR and discusses emerging indications for the use of this diagnostic tool and how they compare with and complement non-invasive or other invasive diagnostic modalities. The manuscript addresses some of the key unanswered questions related to FFR, the potential pitfalls of this tool and discusses future directions of use and research.

The functional SYNTAX score - a huge step forward or research in motion?

In a recent manuscript in the Journal of the American College of Cardiology, the newly introduced "functional SYNTAX score" (FSS) was found to be a better tool to assess the extent and severity of coronary artery disease than the SYNTAX score (SS) and has reclassified 1/3 of the studied cohort into lower-risk categories. Besides being more invasive, costly, and time consuming, FSS still suffers from inherent deficiencies of its own. Like SS, FSS does not incorporate clinical risk predictors and consequently is a suboptimal tool for predicting PCI risk. FSS is not supported by a wealth of contemporary outcome data in a wide range of patient and lesions subsets. Key unanswered questions are whether PCI of hemodynamically significant lesions (FFR <0.80) is superior to optimal medical therapy (OMT) and whether complete revascularization yields considerably better outcomes than partial revascularization. Since partial revascularization is still an option, operational FSS (taking into account only the FSS of lesions subject to PCI) combined with a clinical risk score will probably better predict the procedural risk of the planned PCI.

Ablation of atrial-ventricular junction tissues via the coronary sinus using cryo balloon technology

INTRODUCTION

The coronary sinus (CS) can provide access to targets across and within the atrioventricular (AV) junction.

METHODS

In 12 dogs (32 +/- 3 Kg), cryo balloons (10-19 mm) were applied to regions of the AV junction for 3 minutes at a temperature of -75.9( composite function) +/- 9(composite function)C (ranging -57 to -83). Electrical activity and pacing within the CS were assessed pre and post ablation and at least 3 months later in 9 dogs. In the 3 other dogs, hearts were examined immediately after cryo ablation. CS and circumflex angiography was performed pre and post ablation. The hearts, CS, and Cx were then examined for structural injury. The AV junction was sectioned and the hearts were immersed in Tetrazolium, and the lesions were inspected for transmurality across the AV groove.

RESULTS

In 3/12 dogs the distal CS cryo lesions resulted in inferior ST segment depression that resolved within 5 minutes. There was no arrhythmia or hemodynamic changes. No CS electrical activity was noted post ablation. The pacing threshold increased from 2 +/- 2.3 mA to 7.4 +/- 3.6 mA (p < 0.001). Pathological examination of 3 acute hearts revealed hematomas. There was no pericardial effusion. No evidence of stenosis or thrombosis was seen within the CS and the circumflex artery. After 3 months of recovery, transmural lesions across the AV groove were present in all of the targeted AV regions.

CONCLUSION

Intra-CS cryo balloon ablation is safe and can potentially replace endocardial RF ablation targeting the AV junction and the CS muscular sleeve.