Protective effect of collateral vessels during coronary angioplasty

Assessment of myocardium at risk with computerized vectorcardiography and technetium-99m-sestamibi-single photon emission computed tomography during coronary angioplasty

OBJECTIVE

To compare the myocardium at risk (MAR) as estimated by computerized vectorcardiography (cVCG) with MAR determined by Tc-99m-sestamibi-SPECT using coronary angioplasty as the model for transient transmural ischemia in humans.

METHODS AND RESULTS

In 37 patients with stable angina pectoris, cVCG was recorded continuously during coronary angioplasty. The scintigraphic defect was quantified using an automated software program (CEqual). The ST vector magnitude (ST-VM) and the ST change vector magnitude (STC-VM) correlated well with MAR estimated by scintigraphy, ST-VM (r = 0.71, p < 0.001) and STC-VM (r = 0.84, p < 0.001). All patients with STC-VM <50 microV during occlusion had defects of less than 10% of the left ventricle.

CONCLUSION

1) ST-VM and STC-VM give a reasonable useful estimate of MAR size during transient coronary occlusion. 2) STC-VM <50 microV is a reliable limit to identify patients with MAR size less than 10%. 3) ST-VM does not add information to STC-VM with respect to detection of ischemia. 4) The existence of collateral vessels has great impact on both ST-vector changes and scintigraphic imaging of myocardial ischemia.

The pattern of alteration in flow velocity in the recanalized artery is related to left ventricular recovery in patients with acute infarction and successful direct balloon angioplasty

OBJECTIVES

We evaluated the relationship between alterations in coronary flow velocity during the acute phase of acute myocardial infarction (AMI) and the recovery of left ventricular wall motion in patients who underwent successful primary angioplasty.

BACKGROUND

The status of the coronary microcirculation is the major determinant of the prognosis of patients who have had successful reperfusion after AMI. Animal studies have shown that dynamic changes in regional flow are associated with the extent of infarction. Evaluation of alterations in coronary flow velocity in infarcted arteries may provide information about microcirculatory damage.

METHODS

Flow velocity of the distal anterior descending artery was continuously monitored with the use of a Doppler guide wire immediately after recanalization for 18 +/- 4 h in 19 patients who underwent successful primary angioplasty after anterior AMI. Subjects were divided into two groups on the basis of the time course of alterations in average peak velocity (APV). Group D consisted of patients who had progressive decreases in APV through the next day (n = 9), and Group I comprised patients with an increase in APV after a transient decline (n = 10). Ejection fraction (EF) and regional wall motion (RWM) were assessed by left ventriculography performed on admission and at discharge.

RESULTS

The APV at the end of monitoring was greater in group I than in group D. In group I, EF and RWM were significantly improved at discharge. The change in EF was greater in group I than in group D (17 +/- 9% vs. 4 +/- 9%, p = 0.007), as was the change in RWM (0.96 +/- 0.23 vs. 0.13 +/- 0.36 SD/chord, p < 0.0001).

CONCLUSIONS

The alteration in flow velocity in recanalized infarcted arteries is related to left ventricular recovery. A progressive decrease in velocity after angioplasty implies no reflow, which is associated with a poor recovery of left ventricular function. Reperfusion injury may account in part for this phenomenon.

QRS alterations in body surface potential distributions during percutaneous transluminal coronary angioplasty in single-vessel disease

Body surface QRS potentials were recorded with 63 chest leads in 20 patients with proximal single-vessel disease located on either the left anterior descending coronary artery (n = 10), the right coronary artery (n = 6), or the left circumflex coronary artery (n = 4) before, during, and after percutaneous transluminal coronary angioplasty. In each case, three consecutive inflations of relatively short duration (37 +/- 14 seconds) were carried out. Electrical activity was displayed as unipolar electrograms and body surface potential maps. The total QRS complex duration decreased in 14 of the 20 patients. Focal conduction disturbances were observed in six cases; all six had left anterior descending coronary artery occlusion and two were also accompanied by a clear shortening of the right epicardial breakthrough time. In these two cases, an initial activation loss seemed to be characteristic, whereas in the other four cases, a rather diffuse slowing of intraventricular conduction, especially during the terminal portion of the QRS, could be observed. Individual and group mean isointegral difference body surface potential maps (during-minus-before dilation) were considered valuable for the interpretation of localized changes in intraventricular conduction during percutaneous transluminal coronary angioplasty, and their individual variations could, at least partly, be explained by the presence or absence of collateral circulation. Two different hypotheses are suggested to account for the QRS complex shortening observed during short-term myocardial ischemic injury: (1) coronary artery occlusion delayed activation of the portion of the septal region that is normally activated early during the QRS, and/or (2) coronary artery occlusion increased the speed of propagation within the ventricles. Both of these hypotheses are discussed in light of earlier clinical and experimental results.

Are reciprocal changes a consequence of "ischemia at a distance" or merely a benign electric phenomenon? A PTCA study

The significance of reciprocal ST-segment depression during acute occlusion of an epicardial coronary artery is still actively debated. "Ischemia at a distance" has been implicated in numerous reports. To determine the prevalence and mechanism of reciprocal changes, we recorded 12-lead electrocardiograms (ECG) during balloon inflation in 66 patients undergoing 79 coronary angioplasty (PTCA) procedures. The 38 men and 28 women had a mean age of 59 +/- 12 years. Twenty nine PTCAs were of the dominant right coronary artery (RCA), 24 were of the proximal left anterior descending artery (LAD), 24 of the left circumflex artery (LCF), and 2 of the diagonal branch of the LAD. Primary ST elevation (> or = 1 mm) occurred in 56 (71%) PTCAs, 49 (88%) of which showed reciprocal (> or = 1 mm) ST depression. Reciprocal changes occurred in 15 of 21, 19 of 20, and 14 of 14 PTCAs of the LAD, RCA, and LCF, respectively (p value not significant [NS]) and were common in patients with collateral vessels supplying the arterial bed distal to the site of balloon occlusion (60%). They were equally prevalent in PTCAs of patients with single-vessel disease and patients with multivessel disease (90% vs 82%, p = NS). We conclude that reciprocal changes occur in the majority regardless of the vessel involved or the extent of coronary artery disease, that they usually represent electric phenomena and not remote ischemia, and that "ischemia at a distance" is not a diagnosis that can be made by ECG.

Influence of minimal angiographic visible collateral circulation on myocardial function during PTCA

The potential protective role of angiographically visible minimal collateral circulation in diagnostic angiograms, not reaching or filling the target vessel (RENTROP class 1), on myocardial function during percutaneous transluminal coronary angioplasty (PTCA), was studied in two groups of patients undergoing elective PTCA of the left anterior descending artery (LAD). In the first study group consisting of 22 patients, influence of collateral circulation class 1 on left ventricular regional function was evaluated. In this group, 14 patients showed no angiographic collaterals and 8 patients showed collateral circulation class 1 in diagnostic angiograms. Increase of end-diastolic and end-systolic volume indices as well as decrease of global left ventricular function was not significantly different inpatients with and without such minimal collateral circulation. In patients without collaterals, the decrease of regional left ventricular function was significantly more pronounced in the left anterior length segment (p less than 0.05) and a trend was observed in the anterolateral (p = 0.059) and apical (p = 0.053) segments. In a second group, consisting of 29 patients, hemodynamic parameters were measured and, in addition to grading of collateral circulation in diagnostic angiograms, angiographically visible collateral circulation was estimated during occlusion of the LAD by injecting contrast materials into the right coronary artery. An increase of angiographically visible collaterals during the ischemic period of various degrees was documented in 26 (90%) of 29 patients. Combining patients of both study groups, increase in left ventricular end-diastolic pressure during ischemia was significantly higher (p less than 0.05) in patients without collaterals on diagnostic angiography (n = 34) than in patients with collateral circulation class 1 (n = 14).(ABSTRACT TRUNCATED AT 250 WORDS)

Deterioration in left ventricular performance during early coronary angioplasty after thrombolysis. Evidence for myocardial salvage

To investigate the effects of controlled coronary artery reocclusion after successful thrombolysis, we studied 15 patients during early elective angioplasty of the patent infarct-related artery. Eight patients underwent left anterior descending artery dilation, and the other 7 had right coronary artery dilation. In 13 cases, ST-segment elevation developed during balloon occlusion. In all 15 cases, intravenous digital subtraction left ventriculography during balloon inflation showed that the ejection fraction decreased at least 5% (mean decrease, from 60% to 47%), despite preexisting Q waves overlying the infarct territory in 5 patients. Balloon inflation resulted in decreased apical segmental shortening in all 8 patients who underwent left anterior descending artery dilation; likewise, balloon inflation produced impairment of inferior-wall contraction in all 7 patients who had right coronary artery dilation. In this setting, a deterioration in left ventricular performance indicates that the restoration of coronary patency with thrombolysis has resulted in myocardial salvage. In patients with Q waves, such deterioration suggests that this electrocardiographic abnormality does not necessarily indicate a completed infarction.