Percutaneous therapy of total coronary occlusions is generally more challenging than the treatment of stenotic lesions. It more frequently entails the risk of irreversibly disrupting a protruding plaque, of advancing the wire through a false route, or rarely, of causing coronary perforation. Furthermore, the length of the occlusion is usually either unknown or can only be vaguely estimated during injection into the contralateral coronary artery as a result of distal opacification by collaterals. The procedural difficulty involved in treating total occlusions and the associated risks are more pronounced than treating nonocclusive lesions that are usually easier to cross.1–3 We have consecutively applied a method that enables the demonstration of the lumen beyond a total occlusion in the clinical setting of treating acute and subacute (> 7 days) coronary occlusions. This method, previously advocated for use in chronic total occlusions,1–4 involves crossing the lesion with a soft-tipped guidewire supported by an over-the-wire balloon catheter, followed by the injection of dilute contrast through the balloon under fluoroscopy to achieve distal lumen visualization. Applied to ascertain intraluminal position of the balloon catheter tip, this method has never been systematically evaluated in acute and subacute occlusions. Our objective in this study was to evaluate the safety and sensitivity of this technique by consecutively employing this technique in a large group of patients undergoing percutaneous coronary interventions (PCI) in the setting of an acute occlusion. Patients and Methods Patients. The study included 106 consecutive patients admitted to our hospital from July 2000 to June 2004 for an acute coronary event who underwent coronary angiography and were found to have a total occlusion of a coronary artery that was immediately treated. The study protocol was approved by the local institutional review board. The mean age of all patients was 60 ± 14 years (median 61), with 85 males (80%) and 21 females (20%). Ninety of the patients (85%) were admitted for acute myocardial infarction, and 16 patients (15%) were treated for unstable angina. The prevalence of hypercholesterolemia, smoking, hypertension, diabetes mellitus, and chronic renal failure among the study patients was 51%, 44% (47% including past smoking), 41%, 35%, and 8.7%, respectively. Coronary artery disease involved a single epicardial coronary vessel in 60 patients (57%), 2 vessels in 29 patients (28%), and 3 vessels in 17 patients (16%). Left ventricular systolic function (n = 105) was normal in 50 patients (48%), mildly reduced in 24 (23%), moderately reduced in 20 (19%), and severely reduced in 11 patients (10%). The right coronary artery was the site of the culprit lesion in 55 patients (52%), the left anterior descending in 31 (29%), and the circumflex/marginal artery in 20 (19%) patients. Dilatation was successful in 100 patients (96%). Methods The coronary occlusion was crossed by gentle manipulation of a soft guidewire (e.g., HTF, Guidant Corporation, Indianapolis, Indiana) supported by an over-the-wire (OTW) Maverick™ angioplasty balloon (Boston Scientific, Natick, Massachusetts). The balloon was advanced over the wire to the distal coronary lumen beyond the occlusion. The wire was then withdrawn, blood was slowly aspirated through the catheter via a stopcock to remove any residual air within the connection, and 2 ml of contrast material (1:2 to 1:4 diluted with saline) were injected under fluoroscopy or cine to ascertain intraluminal position of balloon tip and to demonstrate the distal coronary artery lumen. The guidewire (in some cases, a higher-support wire such as the BMW guidewire, Guidant Corporation) was re-introduced into the catheter and the procedure was completed as usual. Sensitivity, specificity, and positive predictive value of the study method were determined according to the following scheme: 1) demonstration of the distal arterial contour by contrast filling, followed by successful dilatation was considered a true positive result; 2) extravasation of contrast after test injection was considered a true negative situation; 3) lack of luminal demonstration by contrast injection of a major coronary artery or its branch, which was later successfully dilated, represented a false negative case; 4) initial contrast filling in a pattern suggesting proper arterial lumen but found later, after failed dilatation to represent extravasation, was considered a false positive event. Results No procedural complications attributed to the study method were encountered. In the initial phase (several of the first 10 study patients), a few air bubbles were sometimes observed in the occluded compartment after contrast injection prior to dilation due to residual air within the connection. This occurrence was not associated with any adverse response. Following this, however, special care was taken to fully aspirate the balloon catheter prior to injection in order to completely eliminate air space, and this phenomenon did not recur. True positive, false positive, true negative, and false negative results were obtained in 89, 3, 7, and 6 patients, respectively. Sensitivity, specificity, positive and negative predictive values of the study method in the present population were 94%, 70%, 97%, and 54%, respectively. Figure 1 shows the stages of the present method including coronary artery occlusion (A), lumen demonstration via balloon (B), occluding lesion length estimate (C), and final result (D). Discussion This study evaluated the method of contrast injection beyond total occlusions for coronary lumen demonstration in acute cardiac patients undergoing an intervention. In addition to ascertaining the intraluminal position of the wire, it may serve to delineate distal arterial contour and to estimate occlusion length. The method previously described during treatment of chronic total occlusions1–4 was shown to be safe in the acute condition, and was not associated with any complications, even in the infrequent case when slight contrast material extravasation occurred. This technique was found in the present study to be highly sensitive, moderately specific, and of high positive predictive accuracy in the acute condition. The implication of these results is that when the distal lumen is positively demonstrated, there is a high probability that proper positioning of the wire will be achieved and that dilatation can be performed safely and successfully. In our experience, the lack of luminal demonstration with successful outcome, or a false negative reading, was probably due to injection in a very distal portion of the culprit artery, or in a smaller secondary branch. Generally, when treating acute occlusions, proper guidewire passage with intraluminal position can be assumed when free guidewire rotation, or its easy advancement, are possible after lesion crossing with slight or no resistance.2 Assurance is gained when the wire follows a clear anatomical course, especially when it enters side branches en route. In such situations the risk of entering a false route or causing a dissection is low, and the present method is usually not necessary. However, when crossing an obstruction is difficult and wire passage distally meets with resistance, there is a real risk of creating a false channel by pushing the wire. It is in these situations that the present method seems to offer a benefit by ensuring proper wire position and conferring enhanced procedural safety. When using this technique, it is the true positive situation, one achieved in the vast majority of cases, that truly reassures the operator. It means that balloon inflation can be achieved with safety and confidence. In the event of a negative injection test result, whether false or true negative, we believe inflation should not be attempted. The preferable action would be to seek a better position for the balloon tip, or to completely withdraw the whole system and start anew. The method requires a small-volume contrast test injection through the angioplasty balloon lumen which may rarely enter a false route, cause a subintimal contrast depot, or extremely rarely, induce extensive dissection.5 However, this is preferable, in our opinion, to a “blind” inflation attempt to achieve patency as practiced by some interventional cardiologists under such circumstances. In such a situation, when there is the possibility of wire tip position within a dissection or a false route, inflation might not only preclude successful treatment of the occluded artery but may actually induce damage. In light of the present data, we think that the OTW balloon should not be dilated within the artery whenever definitive distal vessel visualization is not achieved. With the significant safety conferred by the described method, we are convinced that it should be the standard of care when treating total coronary obstructions. In the present series, no complication attributed to contrast injection beyond the occlusion was encountered. An additional benefit of this method is that the injection of contrast material through the OTW balloon beyond the occlusion may demonstrate the distal interface of the obstructing lesion (see Figures 1B and 1C), or the presence of distal lesions or thrombi. Superimposition of this image with the routine anterograde injection of the occluded artery at the same angle showing proximal interface of blockage (Figure 1A) could yield an estimate of occlusion length (Figure 1C). Utilization of an OTW balloon rather than a rapid exchange system in the initial stage of the procedure enables the recording of the pressure signal,6 which is helpful since we have found repeatedly that a phasic pressure reading indicates intraluminal position of balloon. The subsequent easy exchange of the soft wire used for atraumatic lesion crossing with a stiffer wire more suitable for crossing tough lesions or for stent passage through tortuous and calcified arteries is then easily accomplished. In addition, the described method has the potential value of enabling distal administration of drugs, such as nitroglycerin or adenosine. The use of the present method seems advantageous when utilizing protection devices that may be applied more frequently in the near future in light of evolving interventional practice. These devices, whose use seems to be indicated when treating thrombotic occlusions, are still bulky and could potentially induce significant damage if advanced extraluminally within the arterial wall. We propose the present method as a means to ensure intraluminal position of the guidewire and balloon in order to maintain procedural safety and ensure success. We found this method to be very useful and applicable, to add only a few minutes to the procedure, and to be applicable on a routine basis. Study limitations. Our experience shows that the sensitivity of the technique was lower when applied in very distal portions of the primary artery or in secondary coronary branches, such as the diagonal, the obtuse marginal artery, or right ventricular branch. On several occasions, lumen demonstration was not achieved under these circumstances despite proper positioning of the balloon catheter tip (false negative readings). This could possibly be due to a smaller arterial branch caliber, reducing visualization quality and sensitivity. Conclusion The technique of lumen demonstration by contrast injection through an OTW balloon beyond acute or subacute total obstructions was shown to be a safe and effective method to ascertain proper position of the angioplasty balloon, and occasionally enabled the estimation of lesion length or the identification of lesions distal to the obstruction. Evaluation of the present technique in a group of 106 acute patients yielded a sensitivity of 94%, a specificity of 70%, a positive predictive accuracy of 97%, and a negative predictive accuracy of 54% for intraluminal position of the balloon. This technique was found to be valuable in doubtful situations where determination of the wire position was of crucial importance for achieving procedural success. Our experience showed that this technique requires extra care, patience, and a slight procedural delay. In light of the unfortunate scenario of rapidly passing the wire beyond an occlusion, inflating the balloon and occasionally realizing a major dissection due to an extraluminal position of the wire, we are convinced that the short time delay necessary for implementing the present technique is worthwhile. Acknowledgement. The authors wish to thank Morton Liebowitz, MD, for his expert editorial advice.
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