Novel OCT Flushing Technique for Complex Scenarios: Imaging During Iatrogenic Transient AV Block Induced by Intracoronary Adenosine

Abstract: We report the application of a novel optical coherence tomography (OCT) flushing technique where OCT run was performed during transient complete atrioventricular block induced by intracoronary bolus of adenosine. This technique may allow lower hydraulic force needed for contrast flush and reduce artifacts, with consequently improved OCT imaging in demanding clinical scenarios. 

J INVASIVE CARDIOL 2014;26(11):E146-E148

Key words: imaging studies, optical coherence tomography

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Case Report

A 77-year-old woman with stable angina (Canadian Cardiovascular Society class III) was admitted for elective right coronary artery (RCA) angioplasty. She was on chronic medical therapy for angina, hypertension, and dyslipidemia. Electrocardiogram revealed normal sinus rhythm, 75 beats/min, with non-specific ST-T changes in inferior leads. Echocardiography showed dilated left ventricular cavity without regional wall-motion abnormalities and ejection fraction of 60%; moderate mitral and tricuspid regurgitation was present. Coronary angiography demonstrated 80% ostioproximal stenosis of the RCA, with additional 40% and 60% stenoses at the mid and distal segments, respectively; there was also tight ostial stenosis of the posterolateral (PL) branch (Figure 1A). Since solid support was needed to negotiate severely tortuous RCA anatomy, an Amplatz Left 1 (Medtronic) guiding catheter was chosen. However, catheter manipulation resulted in deep RCA cannulation, and after contrast injection, spiral dissection of the entire RCA was evident (Figure 1B). After several attempts, a Runthrough NS guidewire (Terumo Corporation) was placed in the distal posterior descending artery (PDA), and since the dissection reached the RCA ostium, a 3.5 x 22 mm Pro-Kinetic Energy (Biotronik) bare-metal stent was implanted at 14 atm to prevent it spreading toward the aortic cusp. After covering the anterograde entry of the dissection, a 3.5 x 20 mm Pro-Kinetic Energy bare-metal stent was implanted at 12 atm with distal overlap. Control angiography showed that the proximal part of the dissection was resolved and the PL branch was gone, while trapped intramural hematoma was present in the right ventricular branch and distal RCA. The procedure was terminated. Final angiography revealed segmental changes in the RCA luminogram; the artery was significantly larger and contours were smooth, without any trace of previous atherosclerotic changes in some parts —signs of a false lumen. 

After 1 week, control angiography (Figure 1C) and OCT examination were performed to evaluate the result and to better understanding the vessel structure. A Dragonfly OCT catheter (St Jude Medical) was placed up to the mid, tortuous part of the RCA. A JR6 guiding catheter (Medtronic Vascular) was then used to deliver contrast. The first OCT run was of poor quality due to extreme tortuosity. In addition, the terrain of the recent dissection did not permit satisfactory manual flush (Figure 2A). We decided to try a novel technique. Before contrast flush, an intracoronary bolus of adenosine 300 µg was given and transient complete atrioventricular (AV) block was induced for several seconds. During that period, contrast flush was performed and a significantly better OCT run was achieved (Figure 2B), showing that the ostioproximal part of the stent was clearly true lumen (Figure 3). However, we landed in false lumen distally, and a double lumen was present in at least part of the OCT run. Combining OCT and angiography findings, we concluded that true lumen was covered with stent only in the ostioproximal part of the RCA, while false lumen extended distally till the mid PDA.

Discussion

OCT is a valuable tool for better understanding coronary anatomy, allowing close insights into vessel structure and tailoring treatment. In case of dissection, one must be cautious of the potential hazard of hydraulic injury when the guiding catheter position is very close to an unhealed dissection entry zone. Image quality during OCT run could be impaired for several reasons, such as non-uniform rotational distortion (NURD), out-of-view artifacts, or coronary spasm.¹ In our case, it appears that the vessel was probably distally filled with blood, which could not be properly flushed out with x-ray contrast. Although full undiluted contrast was manually administered, demanding vessel anatomy and a terrain of recent wall rupture made adequate flushing unlikely. As a novel flushing technique, we performed an OCT run after intracoronary bolus administration of 200-400 µg adenosine that was supposed to provoke transient complete AV block. Our first OCT run succeeded in exploring vessel structure from the 15th mm only (Figure 2A); in the second run after adenosine application, without increasing force of the flush, we were able to fully examine the vessel length, with significantly fewer artifacts (Figure 2B). Thus, this technique allowed us to visualize a substantially longer segment of targeted artery. 

Physiological effects of adenosine on the mammalian heart, which consist of transient, reversible slowing of the heart rate (negative chronotropism), impairment of AV conduction (negative dromotropism), and antiarrhythmic effects, were first reported in 1929.² Adenosine suppresses the activity of cardiac pacemakers including the sinus node (SN), AV junction, and His–Purkinje system. An inverse relationship between pacemaker hierarchy and sensitivity to adenosine was observed.³

Coronary blood flow depends on arterial pressure, diastolic time, and small vessel resistance.⁴ Since coronary flow occurs mainly in diastole, diastolic blood pressure and the duration of diastole (heart rate effect) are particularly important. Intramural blood supply, especially in cases of thick-wall left ventricles, occurs through two separate blood vessel types. In 1966, Estes and colleagues termed these the ‘A’ and ‘B’ vessels. The B vessels (perforator type) are quite susceptible to change in the balance between intramyocardial compressive forces and coronary perfusion pressure.⁵ 

We accomplish two goals by giving intracoronary adenosine bolus before OCT run. First, we diminished small-vessel resistance through adenosine effect on coronary microcirculation via  A2A receptors, which play a pivotal role in controlling vasodilation.³ Second, we eliminate intramyocardial compressive forces during systolic contraction by achieving complete, transient AV block via A1 adenosine receptors. By achieving these goals, we significantly decreased the intensity of the hydraulic force needed for contrast flush, and also reduced artifacts. 

Regarding the dosage of adenosine needed to achieve complete AV block, we consulted data from a study performed by Leone and colleagues in 2012. Increasing doses of intracoronary adenosine boluses were given to accomplish maximal hyperemia. Complete AV block was developed in 16% of patients with 60 µg, in 27% with 300 µg and in 23% with 600 µg. Importantly, AV block was always transient and spontaneously reversible, thus, never requiring atropine administration or temporary pacemaker implantation.⁶ In our case, we opted for a 300 µg dose, which resulted in complete and transient AV block. A further dose of 100 µg is advised if complete AV block fails with the initial dose. 

Conclusion

The current case presents a new OCT flushing technique. We believe that this technique may be particularly useful in demanding scenarios for OCT imaging, including tortuous vessels, when good flush is needed for exploring distal parts of the artery, or in the setting of frail vessel wall in the presence of dissection. Further studies are needed to confirm the clinical value of this novel technique.

References

1. Bezerra HG, Costa MA, Guagliumi G, Rollins AM, Simon DI. Intracoronary optical coherence tomography: a comprehensive review. JACC Cardiovasc Interv. 2009;2(11):1035-1046.
2. Drury AN, Szent-Gyorgyi A. The physiological activity of adenine compounds with especial reference to their action upon the mammalian heart. J Physiol. 1929;68(3):213-223.
3. Mustafa SJ, Morrison RR, Teng B, Pelleg A. Adenosine receptors and the heart: role in regulation of coronary blood flow and cardiac electrophysiology. Handb Exp Pharmacol. 2009;(193):161-188.
4. Gorlin R. Regulation of coronary blood flow. Br Heart J. 1971;33(Suppl):9-I4.
5. Estes EH Jr, Entman ML, Dixon HB II, Hackel DB. The vascular supply of the left ventricular wall. Am Heart J. 1966;71(1):58-67.
6. Leone AM, Porto I, De Caterina AR, et al. Intracoronary adenosine versus intracoronary sodium nitroprusside versus intravenous adenosine: the NASCI (Nitroprussiato Versus Adenosina nelle Stenosi Coronariche Intermedie) study. JACC Cardiovasc Interv. 2012;5(4):402-408.

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From the ¹Clinical Center Kragujevac, Cardiology Department, Kragujevac, Serbia; ²Faculty of Medical Sciences, University of Kragujevac, Kragujevac, Serbia; and 3 Clinical Hospital Center Zemun, Cardiology Department, Faculty of Medicine, University of Belgrade, Belgrade, Serbia.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.

Manuscript submitted April 14, 2014, final version accepted April 21, 2014.

Address for correspondence: Miodrag Sreckovic, Kumanovska 5/4, 34000 Kragujevac, Serbia. Email: sreckovic7@gmail.com