Coronary wedge pressure in relation to spontaneously visible and recruitable collaterals

Changes in microvascular resistance following percutaneous coronary intervention - From the ILIAS global registry

BACKGROUND

Microvascular resistance (MR) has prognostic value in acute and chronic coronary syndromes following percutaneous coronary intervention (PCI), however anatomic and physiologic determinants of the relative changes of MR and its association to target vessel failure (TVF) has not been investigated previously. This study aims to evaluate the association between changes in MR and TVF.

METHODS

This is a sub-study of the Inclusive Invasive Physiological Assessment in Angina Syndromes (ILIAS) registry which is a global multi-centre initiative pooling lesion-level coronary pressure and flow data.

RESULTS

Paired pre-post PCI haemodynamic data were available in n = 295 vessels out of n = 828 PCI treated patients and of these paired data on MR was present in n = 155 vessels. Vessels were divided according to increase vs. decrease % in microvascular resistance following PCI (ΔMR % ≤ 0 vs. ΔMR > 0%). Decreased microvascular resistance ΔMR % ≤ 0 occurred in vessels with lower pre-PCI fractional flow reserve (0.67 ± 0.15 vs. 0.72 ± 0.09 p = 0.051), coronary flow reserve (1.9 ± 0.8 vs. 2.6 ± 1.8 p < 0.0001) and higher hyperemic microvascular resistance (2.76 ± 1.3 vs. 1.62 ± 0.74 p = 0.001) and index of microvascular resistance (24.4 IQ (13.8) vs. 15. 8 IQ (13.2) p = 0.004). There was no difference in angiographic parameters between ΔMR % ≤ 0 vs. ΔMR > 0%. In a cox regression model ΔMR % > 0 was associated with increased rate of TVF (hazard ratio 95% CI 3.6 [1.2; 10.3] p = 0.018).

CONCLUSION

Increased MR post-PCI was associated with lesions of less severe hemodynamic influence at baseline and higher rates of TVF at follow-up.

Index of microcirculatory resistance: state-of-the-art and potential applications in computational simulation of coronary artery disease

The dysfunction of coronary microcirculation is an important cause of coronary artery disease (CAD). The index of microcirculatory resistance (IMR) is a quantitative evaluation of coronary microcirculatory function, which provides a significant reference for the prediction, diagnosis, treatment, and prognosis of CAD. IMR also plays a key role in investigating the interaction between epicardial and microcirculatory dysfunctions, and is closely associated with coronary hemodynamic parameters such as flow rate, distal coronary pressure, and aortic pressure, which have been widely applied in computational studies of CAD. However, there is currently a lack of consensus across studies on the normal and pathological ranges of IMR. The relationships between IMR and coronary hemodynamic parameters have not been accurately quantified, which limits the application of IMR in computational CAD studies. In this paper, we discuss the research gaps between IMR and its potential applications in the computational simulation of CAD. Computational simulation based on the combination of IMR and other hemodynamic parameters is a promising technology to improve the diagnosis and guide clinical trials of CAD.

Left Ventricular Unloading Increases the Coronary Collateral Flow Index Before Reperfusion and Reduces Infarct Size in a Swine Model of Acute Myocardial Infarction

Background Unloading the left ventricle and delaying reperfusion reduces infarct size in preclinical models of acute myocardial infarction. We hypothesized that a potential explanation for this effect is that left ventricular (LV) unloading before reperfusion increases collateral blood flow to ischemic myocardium. Methods and Results Acute myocardial infarction was induced by balloon occlusion of the left anterior descending artery for 120 minutes in adult swine, followed by reperfusion for 180 minutes. After 90 minutes of occlusion, animals were assigned to 30 minutes of continued occlusion (n=6) or to 30 minutes of support with either an Impella CP (n=4) or venoarterial extracorporeal membrane oxygenation (n=5) with persistent occlusion. The primary end point was measures of microcirculatory blood flow including the collateral flow index (CFI) during left anterior descending artery occlusion as (P_w-RA)/(P_a-RA), where P_a, P_w, and RA are aortic, coronary wedge, and right atrial pressure, respectively. Infarct size was quantified using triphenyltetrazolium chloride. Compared with continued occlusion, Impella, not venoarterial extracorporeal membrane oxygenation, reduced infarct size relative to the area at risk. Before reperfusion, Impella reduced LV stroke work by 25% and increased the CFI by 75%, but venoarterial extracorporeal membrane oxygenation did not. Among all groups, the change in CFI between 90 and 120 minutes correlated inversely with the change in LV stroke work (r²=0.44, P=0.01) and infarct size (r²=0.41, P=0.02). Conclusions We report for the first time that 30 minutes of LV unloading during coronary occlusion increases the CFI, which correlates inversely with LV stroke work and infarct size. Venoarterial extracorporeal membrane oxygenation failed to increase the CFI and did not reduce infarct size.

Macrophage migration inhibitory factor (MIF) is associated with degree of collateralization in patients with totally occluded coronary arteries

BACKGROUND

Collaterals in patients with coronary artery disease (CAD) limit myocardial infarction and improve survival. Macrophage migration inhibitory factor (MIF) might play a role in collateral development. We aimed this study to evaluate the association of Macrophage migration Inhibitory Factor (MIF) with the extent of collateralization in patients with coronary occlusion.

METHODS AND RESULTS

We consecutively enrolled: a) 40 patients undergoing PCI of a chronic coronary total occlusion (CTO); b) 26 patients with ST-elevation myocardial infarction (STEMI) undergoing primary PCI (pPCI) of the infarct-related artery (IRA); c) 12 control patients undergoing angiography without significant coronary artery disease (CTRL). CTO patients were grouped in high (HCG) or low collateralization group (LCG). STEMI patients were grouped in COLL+ or COLL- group depending on the presence of collaterals to the IRA. Blood sampling was performed from the arterial sheath (SYSTEMIC), and distal to the occlusion (LOCAL). SYSTEMIC and LOCAL levels were significantly different between the 3 groups. A progressive increase in MIF ratio (defined as: % (LOCAL-SYSTEMIC)/SYSTEMIC) was observed (CTRL: -0.5[-23;28] vs. CTO: 4[-19;32] vs. STEMI: 55[37;87], p < 0.01). In CTO, MIF ratio was significantly higher in HCG vs. LCG (68 [45;120] vs. 46 [29;66], p = 0.02). In STEMI, MIF ratio was not different between COLL+ and COLL- patients; however, in COLL+, LOCAL was significantly higher as compared with SYSTEMIC (83 ng/ml [63;100] vs. 67 ng/ml [40;79], p = 0.04).

CONCLUSIONS

Local MIF is significantly associated with the extent of collateralization in both acute and chronic total coronary occlusions.

Acute Hemodynamic Effects of Remote Ischemic Preconditioning on Coronary Perfusion Pressure and Coronary Collateral Blood Flow in Coronary Heart Disease

BACKGROUND

The aim of this study was to assess the acute hemodynamic effects of remote ischemic preconditioning (RIPC) on coronary perfusion pressure and coronary collateral blood flow.

METHODS

A total of 17 patients with coronary heart disease with severe (70%-85%) stenosis in one or two vessels confirmed by angiography were enrolled into this study. They were randomly divided into the RIPC group (9 patients) and the control group (8 patients). Distal pressure of coronary artery stenosis before balloon dilation (non-occlusive pressure, Pn-occl) and distal coronary artery occlusive pressure (Poccl) during balloon dilation occlusion were measured in all patients. The patients in the RIPC group received three cycles of lower limb ischemia-reperfusion preconditioning (5 minutes inflation of a blood pressure cuff, followed by 5 minutes reperfusion). For controls, the cuff was not inflated. After this process, Pn-occl and Poccl were measured again in each patient.

RESULTS

There were no significant differences in angiographic characteristics between the two groups (all p > 0.05). Troponin I (TNI) levels after percutaneous coronary intervention (PCI) were lower in the RIPC group than in the control group (p = 0.004). In the RIPC group, mean Pn-occl and Poccl were significantly increased after RIPC compared to before RIPC [(72.78 ± 10.10) mmHg vs. (79.67 ± 9.79) mmHg, p = 0.002, (20.89 ± 8.61) mmHg vs. (26.78 ± 10.73) mmHg, p = 0.001, respectively].

CONCLUSIONS

RIPC can improve distal coronary perfusion pressure and rapidly increase distal coronary occlusive pressure thereby improving coronary collateral blood flow.

High-Sensitivity C-Reactive Protein Is a Predictor of Coronary Microvascular Dysfunction in Patients with Ischemic Heart Disease

Background

Inflammation and microvascular dysfunction (MVD) are independently associated with adverse cardiovascular outcomes in patients with ischemic heart disease. This study aimed to assess the relationship between inflammation, MVD, and myocardial injury.

Methods

Coronary microvascular function was assessed in 74 patients undergoing percutaneous coronary intervention (PCI) using the index of microvascular resistance (IMR) by a pressure–temperature sensor-tipped wire. Serum high-sensitivity C-reactive protein (hsCRP) level was quantified by rate turbidimetry. Severe MVD was defined as IMR ≥ 30. Pearson correlation was computed to assess the relationships between hsCRP, troponin, and IMR of culprit vessel. Predictors of severe MVD were assessed by regression analysis.

Results

Acute coronary syndromes (ACSs) represented 49% of the total cohort. Study cohort was divided into low C-reactive protein (CRP) (hsCRP < 3 mg/L) and high CRP (hsCRP ≥ 3 mg/L) groups. There was higher representation of smokers (78 vs. 52%), diabetics (39 vs. 18%), and ACS (61 vs. 33%), as well as higher body mass index (29.4 ± 4.6 vs. 27.2 ± 4.1) in the high CRP group. Pre-PCI and post-PCI IMR were significantly elevated in the high CRP group compared to the low CRP group (pre-PCI IMR: 29.0 ± 13.9 vs. 17.4 ± 11.1, p < 0.0001; post-PCI IMR: 23.0 ± 16.8 vs. 15.5 ± 8.4, p = 0.02). Peak troponin levels were significantly raised in the high CRP group (9.96 ± 17.19 vs. 1.17 ± 3.00 μg/L, p = 0.002). There was a strong positive correlation between hsCRP and pre-PCI IMR (r = 0.85, p < 0.0001). Pre- and post-PCI IMR levels were correlated with peak troponin level (r = 0.45, p < 0.0001; r = 0.33, p = 0.005, respectively). Predictors of severe MVD include male gender (OR 3.0), diabetes (OR 3.7), smoking history (OR 4.0), ACS presentation (OR 8.5), and hsCRP ≥ 3 mg/L (OR 5.6).

Conclusion

hsCRP is a significant predictor of MVD while MVD is associated with myocardial injury, supporting the central role of inflammation and MVD in the pathophysiology and complications of coronary artery disease.

Clinical Trial Registration

Australian New Zealand Clinical Trials Registry (ACTRN): 12617000648325. Universal Trial Number (UTN): U1111-1196-2246.

Coronary collaterals provide a constant scaffold effect on the left ventricle and limit ischemic left ventricular dysfunction in humans

Coronary collaterals preserve left ventricular (LV) function during coronary occlusion by reducing myocardial ischemia and may directly influence LV compliance. We aimed to re-evaluate the relationship between coronary collaterals, measured quantitatively with a pressure wire, and simultaneously recorded LV contractility from conductance catheter data during percutaneous coronary intervention (PCI) in humans. Twenty-five patients with normal LV function awaiting PCI were recruited. Pressure-derived collateral flow index (CFI(p)): CFI(p) = (P(w) - P(v))/(P(a) - P(v)) was calculated from pressure distal to coronary balloon occlusion (P(w)), central venous pressure (P(v)), and aortic pressure (P(a)). CFI(p) was compared with the changes in simultaneously recorded LV end-diastolic pressure (ΔLVEDP), end-diastolic volume, maximum rate of rise in pressure (ΔLVdP/dt(max); systolic function), and time constant of isovolumic relaxation (ΔLV τ; diastolic function), measured by a LV cavity conductance catheter. Measurements were recorded at baseline and following a 1-min coronary occlusion and were duplicated after a 30-min recovery period. There was significant LV diastolic dysfunction following coronary occlusion (ΔLVEDP: +24.5%, P < 0.0001; and ΔLV τ: +20.0%, P < 0.0001), which inversely correlated with CFI(p) (ΔLVEDP vs. CFI(p): r = -0.54, P < 0.0001; ΔLV τ vs. CFI(p): r = -0.46, P = 0.0009). Subjects with fewer collaterals had lower LVEDP at baseline (r = 0.33, P = 0.02). CFI(p) was inversely related to the coronary stenosis pressure gradient at rest (r = -0.31, P = 0.03). Collaterals exert a direct hemodynamic effect on the ventricle and attenuate ischemic LV diastolic dysfunction during coronary occlusion. Vessels with lesions of greater hemodynamic significance have better collateral supply.

Collateral pressure and flow in acute myocardial infarction with total coronary occlusion correlate with angiographic collateral grade and creatine kinase levels

BACKGROUND

The validity of angiographic collateral grade according to the Rentrop classification during acute myocardial infarction (AMI) and its relation to flow in occluded coronary arteries before angioplasty have never been evaluated.

METHODS

We assessed the validity of the angiographic collateral grade according to Rentrop classification in relation to collateral pressure and flow beyond occluded coronary arteries during AMI. Pressure distal to coronary artery occlusions before balloon dilatation was measured in 111 patients undergoing angioplasty for AMI. We calculated the collateral flow index (CFI) and compared it to observed Rentrop grade and measured creatine kinase sum.

RESULTS

The values of pressure distal to coronary artery occlusions with respect to collateral grades 0 to 3 were 33 +/- 12, 37 +/- 13, 42 +/- 10, and 60 +/- 14 mm Hg (P < .0001). Overall CFI was 0.35 +/- 0.13 (median 0.33), with CFI values of 0.3 +/- 0.13, 0.33 +/- 0.13, 0.39 +/- 0.1, and 0.57 +/- 0.2 for collateral grades 0 to 3, respectively (P < .0001). Larger creatine kinase elevation (P < .016) and higher white blood cell count (P < .022) were recorded in the lowest tertile CFI compared with highest tertile CFI group; but no difference in the global, regional, or infarct-related regional left ventricular contraction was found.

CONCLUSIONS

These observations demonstrate that the Rentrop classification is valid in AMI patients with occluded coronary arteries and that collaterals are recruited acutely. These collaterals, whose pressure-derived CFI during AMI was shown for the first time to be higher than its value reported in chronic conditions, may limit the immediate myocardial damage or the systemic inflammatory response. No impact on global or regional cardiac contraction was detected in a population where most patients were treated early.

Appraising the pathophysiologic impact of coronary collaterals as measured by fractional flow reserve on symptoms and signs of myocardial ischemia

BACKGROUND

The purpose of coronary revascularization in stable patients is anginal relief, yet there is no linear relationship between stenosis severity and clinical significance. A major factor in this complex lesion-myocardium interaction is collateral flow. We aimed to define which collateral flow cut-offs separate asymptomatic from symptomatic patients during coronary occlusion.

METHODS

Patients undergoing percutaneous transluminal coronary angioplasty for a single stenotic lesion were selected, collaterals were appraised angiographically, and fractional flow reserve was used during prolonged balloon occlusion to measure collateral flow index (FFRcoll). Changes in anginal symptoms, ST-T segment, and left ventricular wall motion were appraised before and during/shortly after balloon dilation. Receiver-operating-characteristic curves and area under the curve were computed to identify the most appropriate FFRcoll cut-offs.

RESULTS

Twenty consecutive patients were enrolled. At baseline, 10 patients had angiographic evidence of collaterals, whereas 10 had no angiographic evidence of collateral flow distal to the target lesion. FFRcoll had an excellent discriminatory performance for the presence of angiographic collaterals (area under the curve = 0.90, P = 0.003), a good discriminatory performance for the occurrence of angina (area under the curve = 0.80, P = 0.025), and a trend toward a good discriminatory performance for the occurrence of asynergy (area under the curve = 0.81, P = 0.06). On the basis of receiver-operating-characteristic curves, an FFRcoll cut-off greater than 0.26 could reliably distinguish patients with adequate collaterals (sensitivity = 0.90, specificity = 0.80), whereas a greater than 0.41 cut-off distinguished patients having angina or wall motion abnormalities from those remaining asymptomatic.

CONCLUSION

This study shows that distal collateral pressure greater than 41% of proximal perfusion pressure protects from anginal symptoms or regional systolic dysfunction during coronary occlusion, whereas a greater than 26% cut-off is more appropriate to identify angiographically evident collaterals ensuring distal myocardial viability.

Myocardial protection with enalaprilat in patients unresponsive to ischemic preconditioning during percutaneous coronary intervention

Cardioprotection due to angiotensin enzyme inhibitors is attributed, at least in part, to the inhibition of bradykinin breakdown and the preconditioning effect of the elevated endogenous bradykinin level. We have previously shown that in patients undergoing percutaneous coronary intervention, one 120-second balloon inflation is insufficient to precondition the heart. The objective of the present study was to examine whether the administration of enalaprilat to these patients results in protection. Twenty patients underwent two 120-second coronary artery occlusions separated by a reperfusion interval of 10 min. Ten patients were given 50 µg·min–1 enalaprilat in an intracoronary infusion between the balloon inflations, whereas the others received an infusion of saline. In the latter control patients, there were no significant differences in ST-segment elevation between the consecutive occlusions (peak ST: 1.61 ± 0.17 vs. 1.61 ± 0.16 mV; time to reach 0.5 mV ST elevation: 16 ± 4 vs. 22 ± 7 s; mean ST: 1.03 ± 0.12 vs. 1.02 ± 0.11 mV). In the patients who received enalaprilat before the second balloon inflation, the ST-segment elevation was significantly less pronounced and slower during the second inflation than during the first (peak ST: 1.80 ± 0.18 vs. 1.41 ± 0.19 mV; time to reach 0.5 mV ST elevation: 18 ± 4 vs. 30 ± 4 s; mean ST: 1.04 ± 0.11 vs. 0.85 ± 0.14 mV). We conclude that enalaprilat administered during percutaneous coronary intervention provides protection to patients who do not have a protective response to the initial balloon inflation.

Effect of intracoronary shunt on right ventricular function during off-pump grafting of dominant right coronary artery with poor collateral

Although numerous studies have validated the efficacy of intracoronary shunt on reducing left ventricular dysfunction during off-pump coronary artery bypass surgery (OPCAB), there is lack of evidence supporting its role on right ventricular (RV) function during right coronary artery (RCA) revascularization. Therefore, we studied the effect of intracoronary shunt during grafting of dominant RCA without visible collateral supply on global RV function using thermodilution method. Forty patients scheduled for multivessel OPCAB with right dominant coronary circulation without collateral supply confirmed by angiography were randomized to RCA revascularization either with a shunt (n=20) or soft snare occlusion (n=20). RV ejection fraction (RVEF) was recorded at baseline, during RCA grafting, and 15 min after reperfusion. Corresponding RV stroke work index (RVSWI) was calculated. RVEF and RVSWI decreased significantly during RCA grafting and returned to baseline values after reperfusion in both groups without any significant differences between the groups. Intracoronary shunt did not exert any beneficial effect on global RV function during RCA grafting, even in the absence of visible collateral supply. Regarding the possibility of graft failure by intracoronary shunt-induced endothelial damage, routine use of intracoronary shunt during RCA grafting is not recommended in patients with preserved biventricular function.

Repeated Balloon Inflations Do Not Diminish ST Segment Elevation even though Coronary Collateral Recruitment Is Promoted in Pigs

OBJECTIVE

Attempts to demonstrate preconditioning during repeated angioplasty balloon inflations (BIs) have not been universally successful. The main obstacle is that the first BI is unreliable, due to the variable degrees of occlusion by the deflated balloon. In the present study, we examined whether ST segment elevation decreases and evaluated its relation to collateral recruitment during repeated angioplasty BIs in the pig.

METHODS AND RESULTS

Twenty male pigs, 7 months old, under general anesthesia, underwent 3 repeated BIs of 120 s, with a 5-min interval between them, in the left anterior descending artery or the right coronary artery. A pressure wave wire was used for the measurement of coronary wedge pressure and to obtain the intracoronary ST segment elevation. Intracoronary ST segment elevation was 1.97 +/- 0.76 mV during the 1st BI, 2.09 +/- 0.82 mV during the 2nd BI and 1.84 +/- 0.82 mV during the 3rd BI (p = n.s.). Coronary wedge pressure was 12 +/- 6, 18 +/- 18 and 20 +/- 20 mm Hg (p < 0.05 vs. 1st BI) during the 3 BIs, respectively.

CONCLUSION

Repeated BIs do not diminish ST segment elevation in the pig model, even though coronary collateral recruitment is promoted.

Coronary collaterals during single-vessel coronary angioplasty: effects of nitroglycerin

BACKGROUND

Although the protective role of collaterals in coronary artery disease (CAD) is well known, the influence of drugs on collateral function remains controversial.

HYPOTHESIS

We aimed to investigate prospectively the prevalence of spontaneously visible and recruitable coronary collaterals in consecutive patients with single-vessel CAD and the effect of systemic administration of nitroglycerin on these types of collaterals during percutaneous transluminal coronary angioplasty (PTCA).

METHODS

Ipsi- and contralateral coronary artery contrast injections were performed before and during PTCA. Simultaneously with balloon occlusion, we measured coronary artery occlusion pressure via the balloon catheter. All measurements were repeated after administration of 0.5 mg of nitroglycerin intravenously.

RESULTS

Of 101 consecutive patients, 24% had spontaneously visible and 30% had recruitable collaterals. Contralateral collaterals were five times more frequent than ipsilateral collaterals. Presence of collaterals was highly associated with the degree of coronary stenosis. Coronary occlusion pressure was higher in patients with than in those without collaterals. Collaterals prevented pain and ischemia during PTCA, and in this respect spontaneously visible collaterals were more effective than recruitable collaterals. There was no effect of systemic administration of nitroglycerin on appearance or occlusion pressure of coronary collaterals.

CONCLUSION

Coronary collaterals were found in more than half of patients with single-vessel CAD, as the prevalence of recruitable collaterals was slightly higher than that of spontaneously visible collaterals. Nitroglycerin did neither recruit nor augment coronary collaterals.

Coronary collateral circulation: the effects of smoking and alcohol

OBJECTIVE

The presence or absence of coronary collaterals is of vital importance during acute ischemia. Smoking and alcohol have been suggested to play a role, but data are scarce. We examined the extent to which smoking and alcohol use affect the presence of coronary collateral circulation.

METHODS

Cross-sectional study in 242 patients, admitted for elective PTCA. Smoking was defined as past or current. Pack years were calculated and categorized into never-smokers (reference-category): <10, 10-19, 20-29, and >or=30 pack years. Alcohol consumption was defined as past or current, and categorized into never-users (reference-category): <1, 1-10, 11-20, and >or=21 units per week (UPW). Collaterals were graded with Rentrop's classification. Coronary collateral presence was defined as Rentrop-grade >or=1.

RESULTS

Current smoking (odds ratio (OR) 4.17; 95% confidence interval (CI) 1.79-9.71) was positively associated, while pack years of smoking was not related. Current alcohol intake showed a J-shaped tendency with coronary collateral presence, while past moderate alcohol consumption was inversely associated (OR 0.19; 95% CI 0.04-0.98).

CONCLUSIONS

Smoking and (to some extent) alcohol use are associated with collateral presence. The results support the view that life-style factors may affect the formation of coronary collaterals in patients with ischemic cardiac disease.

Cardiac ischemic score determines the presence of coronary collateral circulation

PURPOSE

The presence of coronary collaterals is of vital importance during acute ischemia, however, marked interindividual variability exists. We examined the extent to which the burden of cardiac ischemia, expressed as a cardiac ischemic score, affects coronary collateral presence.

METHODS

Cross-sectional study in 244 patients, admitted for elective coronary angioplasty. Collaterals were graded with Rentrop's classification. Coronary collateral presence was defined as Rentrop-grade > or =1. The cardiac ischemic score (range 0-4) was calculated by adding 1 point for each of the following four clinical factors present: angina pectoris on exertion, angina pectoris during emotions, previous myocardial infarction, and previous coronary intervention. These four clinical factors were chosen because they can be easily assessed in every patient. We used logistic regression with adjustment for gender, age, hypertension, diabetes mellitus, and hyperlipidemia.

RESULTS

The extent of the cardiac ischemic score (odds ratio 1.8 per score-point; 95% confidence interval 1.3-2.5) was strongly associated with coronary collateral presence. Additional adjustment for multivessel coronary disease left the relation essentially unchanged. Also, if the definition of collateral presence was limited to Rentrop-grade 2 and 3, results were effectively the same.

CONCLUSION

The extent of the cardiac ischemic score determines the presence of coronary collaterals, and may provide a new index for simple assessment of collateral vascular development.

High blood pressure is inversely related with the presence and extent of coronary collaterals

Patients with hypertension have an increased case fatality during acute myocardial infarction (MI). Coronary collateral (CC) circulation has been proposed to reduce the risk of death during acute ischaemia. We determined whether and to which degree high blood pressure (BP) affects the presence and extent of CC circulation. A cross-sectional study in 237 patients (84% males), admitted for elective coronary angioplasty between January 1998 and July 2002, was conducted. Collaterals were graded with Rentrop's classification (grade 0-3). CC presence was defined as Rentrop-grade > or =1. BP was measured twice with an inflatable cuff manometer in seated position. Pulse pressure was calculated by systolic blood pressure (SBP)-diastolic blood pressure (DBP). Mean arterial pressure was calculated by DBP+1/3 x (SBP-DBP). Systolic hypertension was defined by a reading > or =140 mmHg. We used logistic regression with adjustment for putative confounders. SBP (odds ratio (OR) 0.86 per 10 mmHg; 95% confidence interval (CI) 0.73-1.00), DBP (OR 0.67 per 10 mmHg; 95% CI 0.49-0.93), mean arterial pressure (OR 0.73 per 10 mmHg; 95% CI 0.56-0.94), systolic hypertension (OR 0.49; 95% CI 0.26-0.94), and antihypertensive treatment (OR 0.53; 95% CI 0.27-1.02), each were inversely associated with the presence of CCs. Also, among patients with CCs, there was a graded, significant inverse relation between levels of SBP, levels of pulse pressure, and collateral extent. There is an inverse relationship between BP and the presence and extent of CC circulation in patients with ischaemic heart disease.

Collateral-flow measurements in humans by myocardial contrast echocardiography: validation of coronary pressure-derived collateral-flow assessment

AIMS

Myocardial blood flow (MBF) is the gold standard to assess myocardial blood supply and, as recently shown, can be obtained by myocardial contrast echocardiography (MCE). The aims of this human study are (i) to test whether measurements of collateral-derived MBF by MCE are feasible during elective angioplasty and (ii) to validate the concept of pressure-derived collateral-flow assessment.

METHODS AND RESULTS

Thirty patients with stable coronary artery disease underwent MCE of the collateral-receiving territory during and after angioplasty of 37 stenoses. MCE perfusion analysis was successful in 32 cases. MBF during and after angioplasty varied between 0.060-0.876 mL min(-1) g(-1) (0.304+/-0.196 mL min(-1) g(-1)) and 0.676-1.773 mL min(-1) g(-1) (1.207+/-0.327 mL min(-1) g(-1)), respectively. Collateral-perfusion index (CPI) is defined as the rate of MBF during and after angioplasty varied between 0.05 and 0.67 (0.26+/-0.15). During angioplasty, simultaneous measurements of mean aortic pressure, coronary wedge pressure, and central venous pressure determined the pressure-derived collateral-flow index (CFI(p)), which varied between 0.04 and 0.61 (0.23+/-0.14). Linear-regression analysis demonstrated an excellent agreement between CFI(p) and CPI (y=0.88 x +0.01; r(2)=0.92; P<0.0001).

CONCLUSION

Collateral-derived MBF measurements by MCE during angioplasty are feasible and proved that the pressure-derived CFI exactly reflects collateral relative to normal myocardial perfusion in humans.

Ultrasound imaging versus morphopathology in cardiovascular diseases. Coronary collateral circulation and atherosclerotic plaque

This review article is aimed at comparing the results of histopathological and clinical imaging studies to assess coronary collateral circulation in humans. The role of collaterals, as emerging from morphological studies in both normal and atherosclerotic coronary vessels, is described; in addition, present role and future perpectives of echocardiographic techniques in assessing collateral circulation are briefly summarized.

Presence of the metabolic syndrome does not impair coronary collateral vessel formation in patients with documented coronary artery disease

OBJECTIVE

The metabolic syndrome confers an increased risk for cardiovascular morbidity and mortality. The presence of coronary collaterals may have beneficial effects during myocardial ischemia and may improve cardiovascular outcome in patients with coronary artery disease. Impaired collateral formation could be one of the reasons for the increased cardiovascular risk in patients with the metabolic syndrome. The aim of the present study was to determine the influence of the metabolic syndrome and insulin resistance on the presence of coronary collaterals.

RESEARCH DESIGNS AND METHODS

We conducted a cross-sectional study in 227 patients referred for elective percutaneous transluminal coronary angioplasty to the University Medical Centre Utrecht. The metabolic syndrome was diagnosed according to Adult Treatment Panel III, and homeostasis model assessment of insulin resistance (HOMA-IR) and quantitative insulin sensitivity check index (QUICKI) were used to quantify insulin resistance. Coronary collaterals were graded with Rentrop's classification. Rentrop grade >/=1 indicated the presence of collaterals. Results were adjusted for age, sex, and severity of coronary artery disease.

RESULTS

A total of 103 patients (45%) were diagnosed with the metabolic syndrome. There was no association between the metabolic syndrome and the presence of coronary collateral formation (odds ratio [OR] 1.2 [95% CI 0.7-2.0]). Also, the degree of insulin resistance was not related to the presence of coronary collaterals. The OR for HOMA-IR (highest versus lowest tertile) was 0.7 (0.3-1.5) and for QUICKI (lowest versus highest tertile) 0.8 (0.4-1.6).

CONCLUSIONS

The metabolic syndrome and insulin resistance are not related to the presence of coronary collaterals in patients with documented coronary artery disease.

Collateral vessel physiology and functional impact–in vivo assessment of collateral channels

The existence and recruitment of collateral vessels within the coronary circulation may account for the tremendous variability in presentation, symptoms and outcome in patients with coronary atherosclerosis. Multiple episodes of ischemia have been found to produce the stimuli necessary for the growth of new vessels which result in collateral blood flow. Furthermore, there is also a subset of patients with readily recruitable collateral vessels that function to limit myocardial necrosis during an acute ischemic event. Promising early studies have utilized angiogenic growth factors as a means to stimulate collateral growth, bringing a renewal interest in their assessment and significance. We review, in brief, the significance and understanding of the development of coronary collaterals as well as the available means to assess them.

Washout collaterometry: a new method of assessing collaterals using angiographic contrast clearance during coronary occlusion

OBJECTIVE

To investigate the hypothesis that the time to washout of radiographic contrast medium trapped distal to an occluded collateral receiving vessel is inversely related to collateral flow, and that this provides an accurate method for characterising coronary collaterals.

METHODS

An intracoronary pressure derived collateral flow index was determined in 54 patients undergoing percutaneous transluminal coronary balloon angioplasty (PTCA). The study group was subdivided according to whether the collateral vessels were sufficient (n = 17) or insufficient (n = 37) to prevent ECG signs of myocardial ischaemia during PTCA. Washout collaterometry-an angiographic washout method-was carried out simultaneously; after injection of radiographic contrast medium into the collateral receiving vessel followed immediately by vascular occlusion, the number of heart beats was counted until approximately half the length of the epicardial vessel was cleared of contrast.

RESULTS

The collateral flow index was higher (0.28 (0.09) v 0.12 (0.07); p < 0.0001) and the contrast washout time shorter (8.0 (2.9) v 17.5 (6.7) heart beats; p < 0.0001) in patients with sufficient versus insufficient collaterals. There was an inverse correlation between contrast washout time and collateral flow index (r = 0.72, p < 0.0001). Washout of contrast distal to the occluded vessel within 11 heart beats correctly determined sufficient and insufficient collaterals with 88% sensitivity and 81% specificity.

CONCLUSIONS

Washout collaterometry is a new radiographic contrast washout method based on the inverse relation between collateral flow and the time to clearance of radiographic dye injected into the ipsilateral vessel during PTCA. It appears to be an accurate method of characterising coronary collateral vessels.

Quantitative contrast echocardiographic assessment of collateral derived myocardial perfusion during elective coronary angioplasty

OBJECTIVE

To determine whether myocardial contrast echocardiography can be used to quantify collateral derived myocardial flow in humans.

METHODS

In 25 patients undergoing coronary angioplasty, a collateral flow index (CFI) was determined using intracoronary wedge pressure distal to the stenosis to be dilated, with simultaneous mean aortic pressure measurements. During balloon occlusion, echo contrast was injected into both main coronary arteries simultaneously. Echocardiography of the collateral receiving myocardial area was performed. The time course of myocardial contrast enhancement in images acquired at end diastole was quantified by measuring pixel intensities (256 grey units) within a region of interest. Perfusion variables, such as background subtracted peak pixel intensity and contrast transit rate, were obtained from a fitted gamma variate curve.

RESULTS

16 patients had a left anterior descending coronary artery stenosis, four had a left circumflex coronary artery stenosis, and five had a right coronary artery stenosis. The mean (SD) CFI was 19 (12)% (range 0-47%). Mean contrast transit rate was 11 (8) seconds. In 17 patients, a significant collateral contrast effect was observed (defined as peak pixel intensity more than the mean + 2 SD of background). Peak pixel intensity was linearly related to CFI in patients with a significant contrast effect (p = 0.002, r = 0.69) as well as in all patients (p = 0.0003, r = 0.66).

CONCLUSIONS

Collateral derived perfusion of myocardial areas at risk can be demonstrated using intracoronary echo contrast injections. The peak echo contrast effect is directly related to the magnitude of collateral flow.

Intermediate coronary artery stenosis: evidence-based decisions in interventions to avoid the oculostenotic reflex

The prevalence of intermediate coronary artery stenosis (defined as a diameter stenosis of 40% to 70%) is quite large in patients undergoing PTCA. The coronary angiogram is considered the 'gold standard' for the definition of coronary anatomy, in spite of various limitations associated with its use. In recent years, sensor tipped guidewire based methods of physiologic assessment of stenosis severity, like myocardial fractional flow reserve, and poststenotic coronary flow reserve had established their role in the decision making in catheterization laboratory. The decision making should combine morphologic and physiologic assessment as better evidence based approach in guiding therapy to avoid the 'oculostenotic reflex'.

Exercise-induced U-wave alterations as a marker of well-developed and well-functioning collateral vessels in patients with effort angina

OBJECTIVES

We sought to determine whether exercise-induced U-wave alterations are observed in association with well-developed and well-functioning collateral vessels.

BACKGROUND

Although exercise-induced electrocardiographic (ECG) U-wave alterations including negative and prominent U waves have been established as a marker of significant or critical narrowing of a major coronary artery, the relation between this finding and the degree of collateral development has not yet been determined.

METHODS

Patients with stable effort angina were divided into two groups according to the presence (group A, n = 46) or absence (group B, n = 79) of exercise-induced either negative or prominent U waves in the precordial leads; the clinical profiles, coronary angiographic findings and also ischemic status during 60 s of coronary balloon occlusion were compared between the two groups.

RESULTS

The incidence of severe angina (CCS [Canadian Cardiovascular Society] class III or IV) was higher (p < 0.05) in group A (52%) than in group B (32%) patients. Good collateral vessels (Rentrop grade 2 or 3) into the perfusion territory of the culprit vessel were observed more frequently (p < 0.05) in group A (70%) than in group B (43%) patients. Coronary balloon angioplasty was carried out in 23 patients of group A and 40 patients of group B. Both ischemic ST changes (52% vs. 85%) and angina (57% vs. 80%) during balloon inflation were less (p < 0.05) frequently observed in group A than in group B. The incidence of no apparent myocardial ischemia with ST deviation or angina during the balloon inflation was higher (p < 0.05) in group A (39%) than in group B (10%) patients. In the prediction of the absence of myocardial ischemia during balloon inflation by the presence of exercise-induced U-wave alterations, the sensitivity was 69% (9/13) and the specificity was 72% (36/50) in the study patients.

CONCLUSIONS

Exercise-induced U-wave alterations are a marker for well-developed collateral circulation in patients with stable but severe effort angina. This finding is also highly predictive of the absence of myocardial ischemia during transient coronary balloon occlusion and possibly of low-risk for development of acute myocardial infarction or hemodynamic instability upon abrupt closure of the culprit coronary artery.

Is the development of myocardial tolerance to repeated ischemia in humans due to preconditioning or to collateral recruitment?

OBJECTIVES

The purpose of this study in patients with quantitatively determined, poorly developed coronary collaterals was to assess the contribution of ischemic as well as adenosine-induced preconditioning and of collateral recruitment to the development of tolerance against repetitive myocardial ischemia.

BACKGROUND

The development of myocardial tolerance to repeated ischemia is nowadays interpreted to be due to biochemical adaptation (i.e., ischemic preconditioning).

METHODS

In 30 patients undergoing percutaneous transluminal coronary angioplasty, myocardial adaptation to ischemia was measured using intracoronary (i.c.) electrocardiographic (ECG) ST segment elevation changes obtained from a 0.014-in. (0.036 cm) pressure guidewire positioned distal to the stenosis during three subsequent 2-min balloon occlusions. Simultaneously, an i.c. pressure-derived collateral flow index (CFI, no unit) was determined as the ratio between distal occlusive minus central venous pressure divided by the mean aortic minus central venous pressure. The study patients were divided into two groups according to the pretreatment with i.c. adenosine (2.4 mg/min for 10 min starting 20 min before the first occlusion, n = 15) or with normal saline (control group, n = 15).

RESULTS

Collateral flow index at the first occlusion was not different between the groups (0.15 +/- 0.10 in the adenosine group and 0.13 +/- 0.11 in the control group, p = NS), and it increased significantly and similarly to 0.20 +/- 0.14 and to 0.19 +/- 0.10, respectively (p < 0.01) during the third occlusion. The i.c. ECG ST elevation (normalized for the QRS amplitude) was not different between the two groups at the first occlusion (0.25 +/- 0.13 in the adenosine group, 0.25 +/- 0.19 in the control group). It decreased significantly during subsequent coronary occlusions to 0.20 +/- 0.15 and to 0.17 +/- 0.13, respectively. There was a correlation between the change in CFI (first to third occlusion; deltaCFI) and the respective ST elevation shift (deltaST): deltaST = -0.02 to 0.78 x deltaCFI; r = 0.54, p = 0.02.

CONCLUSIONS

Even in patients with few coronary collaterals, the myocardial adaptation to repetitive ischemia is closely related to collateral recruitment. Pharmacologic preconditioning using a treatment with i.c. adenosine before angioplasty does not occur. The variable responses of ECG signs of ischemic adaptation to collateral channel opening suggest that ischemic preconditioning is a relevant factor in the development of ischemic tolerance.

Quantification of collateral flow in humans: a comparison of angiographic, electrocardiographic and hemodynamic variables

OBJECTIVES

Evaluation of collateral vascular circulation according to hemodynamic variables and its relation to myocardial ischemia.

BACKGROUND

There is limited information regarding the hemodynamic quantification of recruitable collateral vessels.

METHODS

Angiography of the donor coronary artery was performed before and during balloon coronary occlusion in 63 patients with one vessel disease. Patients were divided into groups of those with an absence of collateral vessels (group 1, n = 10), those with recruitable collateral vessels (group 2, n = 23) and those with spontaneously visible collateral vessels (group 3, n = 30). During balloon inflation the coronary wedge/aortic pressure ratio (Pw/Pao) was determined as were collateral blood flow velocity variables, using a 0.014" Doppler guide wire. Myocardial ischemia was defined as > or =0.1 mV ST-shift on a 12 lead electrocardiogram at 1 min coronary occlusion.

RESULTS

Myocardial ischemia was present in all patients of group 1, in 14 patients of group 2 and in 3 patients of group 3. Recruitable collateral flow without ischemia showed similar hemodynamic values as in group 3 while these values were similar to group 1 in regard to the presence of recruitable collateral vessels showing ischemia. Logistic regression analysis revealed both Pw/Pao and Vi(col) as independent predictors for the function of collateral vessels.

CONCLUSIONS

Hemodynamic variables of collateral vascular circulation are better markers of the functional significance of collateral vessels than is coronary angiography. The total collateral blood flow velocity integral and coronary wedge/aortic pressure ratio are good and independent predictors of the function of collateral vessels producing complementary information.

Effect of coronary occlusion on left ventricular function with and without collateral supply during beating heart coronary artery surgery

OBJECTIVE

To study the effects of coronary occlusion and collateral supply on left ventricular (LV) function during beating heart coronary artery surgery.

DESIGN

Prospective intraoperative study, performed at baseline, during wall stabilisation, coronary artery occlusion, and 2 and 10 minutes after reperfusion. Transoesophageal M mode echocardiograms, simultaneous high fidelity LV pressure, and thermodilution cardiac output were measured. LV anterior wall thickening, thinning velocities, thickening fraction, regional work, and power production were derived. Asynchrony during the isovolumic periods was quantified as cycle efficiency.

SETTING

Tertiary referral cardiac centre.

PATIENTS

14 patients with stable angina, mean (SD) age 62 (7) years, undergoing left anterior descending artery grafting using the "Octopus" device.

RESULTS

Collaterals were absent in nine patients and present in five. Epicardial stabilisation did not affect LV function. Results are expressed as mean (SD). Coronary occlusion (15.6 (2) minutes) depressed anterior wall thickening (1.4 (0.6) v 2.6 (0.6) cm/s) and thinning velocities (1.4 (0.5) v 3.0 (0.6) cm/s), regional work (2.2 (0.8) v 4.6 (0.6) mJ/cm2), and power (21 (4) v 33 (5) mW/cm2) in patients without collaterals (p < 0.05 for all), but only wall thinning (3.5 (0.5) v 4.8 (0.5) cm/s, p < 0.05) in patients with collaterals. All returned to baseline within 10 minutes of reperfusion. Cycle efficiency and regional work were impaired at baseline and fell during occlusion, regardless of collaterals. Within 10 minutes of reperfusion both had increased above baseline.

CONCLUSIONS

Coronary occlusion for up to 15 minutes during beating heart coronary artery surgery depressed standard measurements of systolic and diastolic anterior wall function in patients without collaterals, but only those of diastolic function in patients with collaterals. Regional synchrony decreased in both groups. All disturbances regressed within 10 minutes of reperfusion.

Coronary collateral quantitation in patients with coronary artery disease using intravascular flow velocity or pressure measurements

OBJECTIVES

This study evaluated two methods for the quantitative measurement of collaterals using intracoronary (IC) blood flow velocity or pressure measurements.

BACKGROUND

The extent of myocardial necrosis after coronary artery occlusion is substantially influenced by the collateral circulation. So far, qualitative methods have been available to assess the human coronary collateral circulation, thus restraining the conclusive investigation of, for example, therapies to promote collateral development.

METHODS

Fifty-one patients with a coronary artery stenosis to be treated by percutaneous transluminal coronary angioplasty (PTCA) were investigated using IC PTCA guidewire-based Doppler and pressure sensors positioned distal to the stenosis. Simultaneous measurements of aortic pressure, IC velocity and pressure distal to the stenosis during and after PTCA provided the variables for calculating collateral flow indices (CFIv and CFIp) that express collateral flow as a fraction of flow via the patent vessel. Both CFIv and CFIp were compared with conventional methods for collateral assessment, among them ST-segment changes >1 mm on IC and surface electrocardiogram (ECG) at PTCA. Also, CFIv and CFIp were compared with each other.

RESULTS

In 11 patients without ECG signs of ischemia during PTCA (sufficient collaterals), relative collateral flow amounted to 46% as determined by Doppler and pressure wire. Patients with insufficient collaterals (n=40) had relative collateral flow values of 18%. Using a threshold of CFI=30%, sufficient and insufficient collaterals could be diagnosed with 100% sensitivity and 93% specificity by IC Doppler, and 75% sensitivity and 92% specificity by IC pressure measurements. The agreement between Doppler and pressure measurements was good: CFIv=0.08 + 0.8 CFIp, r=0.80, p=0.0001.

CONCLUSIONS

Intracoronary flow velocity or pressure measurements during routine PTCA represent an accurate and, at last, quantitative method for assessing the coronary collateral circulation in humans.

Long-term physical exercise and quantitatively assessed human coronary collateral circulation

OBJECTIVES

This prospective, cross-sectional study sought to determine an association between the level of long-term physical activity as well as other clinical and angiographic variables and an index of collateral flow to the vascular region undergoing percutaneous transluminal coronary angioplasty (PTCA).

BACKGROUND

There is limited and conflicting information about the effect of physical exercise on the coronary collateral circulation in humans, partly because previous studies lacked a quantitative means of assessing collateral channels.

METHODS

In 79 patients (mean [+/-SD] age 58 +/- 10 years) with coronary artery disease undergoing PTCA (no transmural myocardial infarction), a coronary collateral flow index was determined as the ratio between the intracoronary (IC) distal flow velocity time integral during (Vi(occl)[cm]) and after (Vi(occl) [cm]) PTCA of the stenosis. Vi(occl)/Vi(occl) was measured by a 0.014-in. Doppler guide wire, from which an IC electrocardiogram (ECG) was also recorded. Patients without ECG ST-T wave changes during PTCA were considered to have sufficient collateral channels (n = 29); those with ST-T wave changes were considered to have insufficient collateral channels (n = 50). The level of long-term physical activity was determined by a structured interview (score from 1 to 4). Univariate and multivariate analyses were used to find associations between physical activity as well as 30 other clinical and angiographic variables and the collateral flow index.

RESULTS

Long-term physical activity during leisure time, but not during work hours, and the severity of the stenosis undergoing PTCA were found to be independently and directly associated with sufficient versus insufficient collateral channels and with Vi(occl) Vi(occl) (leisure time physical activity [LTPA] score 3.3 +/- 0.9 vs. 2.4 +/- 1.0, p = 0.0002; percent diameter stenosis 88 +/- 12% vs. 80 +/- 14%, p = 0.001; Vi(occl)/Vi(occl) = 0.1 +/- 0.1 LTPA score, p = 0.0002 for trend).

CONCLUSIONS

In patients with coronary artery disease, the level of long-term physical activity during leisure time and the severity of the stenosis undergoing PTCA are directly associated with the quantitative degree of collateral flow.

Correlations between recruitable coronary collateral flow velocities, distal occlusion pressure, and electrocardiographic changes in patients undergoing angioplasty

Direct assessment of coronary collateral flow has been difficult in humans. The goal of this study was to correlate the magnitudes and waveform characteristics of recruitable coronary collateral flow velocity measured with Doppler guidewire with other hemodynamic and functional indexes of collateral circulation in patients during angioplasty. Twenty-six patients [age 60 +/- 10 (SD) years] were studied for measurements of flow velocity at the distal segment of the dilated vessel. Collateral flow signals were demonstrated in 18 patients (69%) during balloon inflation. There was a weak yet significant positive correlation between the magnitude of collateral flow velocity and distal occlusion pressure (p < 0.01). The sum of ischemic ST elevation on the 12-lead electrocardiogram was inversely correlated with distal occlusion pressure, but not with the magnitude of collateral flow velocity. Subgroup analysis between patients with (n = 18) and without (n = 8) ST elevation during balloon inflation revealed higher collateral flow velocity signals (p < 0.0001) and greater systolic components of collateral flow in the latter group (p < 0.0001). Thus, functionally significant coronary collaterals showed greater velocity signals and systolic predominance in flow pattern. The functional capacity of human coronary collaterals may be semiquantitated using the Doppler guidewire technique.

Ischemic preconditioning in unstable coronary syndromes: evidence for time dependence

OBJECTIVES

We hypothesized a time-dependent relation between angina occurring spontaneously before percutaneous transluminal coronary angioplasty (PTCA) and the likelihood of an ischemic response during initial balloon occlusion. We further hypothesized that the ability to elicit the "classic" mode of PTCA-related preconditioning would vary with the interval from clinical angina to PTCA.

BACKGROUND

Antecedent angina represents a potential for myocardial preconditioning in unstable ischemic coronary syndromes.

METHODS

We studied 67 patients with Braunwald class III unstable coronary syndromes undergoing PTCA. The interval between the last spontaneous episode of angina preceding PTCA and initial balloon inflation was categorized as follows: 0 to 6 h; 6 to 12 h; 12 to 24 h; and >24 h.

RESULTS

Across the various intervals, there was a significant difference (p = 0.004) in the proportion of patients with an absent ischemic response during the first balloon inflation (0 to 6 h, 50%; 6 to 12 h, 35%; 12 to 24 h, 23%; and >24 h, 4%). There was, however, no difference between the first and second inflations in the proportion of patients with a diminished ischemic response until 6 to 12 h (p = 0.017) had elapsed since the last spontaneous episode of angina. Patients whose angina last occurred >24 h before the first inflation showed the greatest inducibility of PTCA-related preconditioning.

CONCLUSIONS

Strong evidence exists for the occurrence of ischemic preconditioning in unstable coronary syndromes. Although the protective effect of spontaneous angina appears to wane beyond 6 h, recovery of preconditioning occurs from 6 to 12 h. Thus, preconditioning can be reinduced during PTCA with a marked potentiation of the effect at 24 h. This suggests an underlying time-dependent mechanism with a physiologic "half-life" of 6 to 12 h.

Symptomatic reinfarctation of a previously silent myocardial region four months after successful reperfusion--a case report

Coronary collateral circulation helps to preserve myocardial perfusion distal to severely stenotic or totally obstructed coronary arteries. The presence or absence of angina pectoris and the state of myocardial function depend on the extent of collateralization and its functional contribution to myocardial blood flow. Clinical and experimental observations have suggested that newly developed collaterals usually remain even after successful revascularizaton. The authors present a case of a patient with extensive intercoronary collaterals and hibernating myocardium after an acute inferior wall myocardial infarction who underwent successful percutaneous transluminal coronary angioplasty of a totally obstructed, dominant right coronary artery and then experienced extensive reinfarction following reocclusion 4 months later. This case demonstrates failure of extensive collaterals to prevent acute myocardial infarction.

Comparison of collateral vascular responses in the donor and recipient coronary artery during transient coronary occlusion assessed by intracoronary blood flow velocity analysis in patients

OBJECTIVES

This study was designed to evaluate the hemodynamic variables of the collateral circulation during acute coronary occlusion.

BACKGROUND

There is limited information on the physiology of the collateral circulation in coronary artery disease.

METHODS

Angiography of the contralateral donor artery was performed before and during balloon coronary occlusion in 57 patients with one-vessel disease. Recruitable collateral flow was assessed during coronary occlusion by blood flow analysis of the contralateral donor artery (n = 19) or the ipsilateral recipient artery (n = 15), or both (n = 23), using a Doppler catheter or guide wire. Ischemia was evaluated by the ST segment shift (> or = 0.1 mV) on a 12-lead electrocardiogram at 1 min of coronary occlusion.

RESULTS

The presence (n = 39), compared with the absence (n = 18), of recruitable collateral vessels was associated with an increase of blood flow velocity in the donor artery (20 +/- 19% vs. 4.8 +/- 5.9% [mean +/- SD], p = 0.003) and the recipient artery (velocity integral 7.2 +/- 5.5 vs. 2.8 +/- 2.2 cm, p = 0.02) related to a reduced relative collateral vascular resistance (9.2 +/- 10 vs. 20 +/- 11, p = 0.003). Collateral flow in the donor artery yielded a similar predictive value for recruitability of collateral vessels as collateral flow determined in the recipient artery or the coronary wedge/aortic pressure ratio (areas under the receiver operating characteristics curves 0.76 +/- 0.07, 0.78 +/- 0.08, 0.77 +/- 0.07, respectively, p = NS). Collateral flow in the recipient artery was a better predictor for ischemia than collateral flow in the donor artery or angiographic grading of collateral vessels (areas 0.90 +/- 0.05, 0.64 +/- 0.10, 0.73 +/- 0.07, respectively, p < 0.05).

CONCLUSIONS

Coronary blood flow velocity analysis of the donor and recipient coronary arteries can characterize the dynamics of the collateral circulation during acute coronary occlusion. The protective effect of recruitable collateral vessels relates to an increase of flow in the donor and recipient coronary arteries due to a reduced collateral vascular resistance. This study underscores the importance of physiologic variables for the evaluation of the function of recruitable collateral vessels.

Comparison of myocardial contrast echocardiography and coronary angiography for assessing the acute protective effects of collateral recruitment during occlusion of the left anterior descending coronary artery at the time of elective angioplasty

To assess the immediate change in collateral flow distribution within the occluded myocardium and the acute protective effects on myocardial ischemia after coronary occlusion, myocardial contrast echocardiography (MCE) was performed in 15 patients with normal left ventricular function undergoing elective coronary angioplasty of the left anterior descending artery, and the results were compared with those obtained from coronary angiography (CA). The sonicated or nonsonicated contrast material was injected into the right coronary artery before and during coronary occlusion and collaterals were graded on a 4-point scale (none = 0 to good = 3). Development of subjective anginal symptoms, ST-segment shift and wall motion abnormality during coronary occlusion were graded on a 4-point scale (none = 0 to severe = 3). Both MCE and CA detected a significant development in collateral flow during coronary occlusion. There was no significant correlation between MCE and CA collateral grades before or during coronary occlusion. The collateral flow assessed with MCE was inversely but significantly correlated with development of subjective anginal symptoms (r(s) = -0.70, p <0.01), ST-segment shift (r(s) = -0.78, p < 0.005) or wall motion abnormality (r(s) = -0.91, p < 0.001) during coronary occlusion. In contrast, the angiographic collateral flow was not correlated with development of anginal symptoms (r(s) = -0.46, p = 0.10), ST-segment shift (r(s) = -0.41, p = 0.14), or wall motion abnormality (r(s) = -0.26, p = 0.35). The present study suggested that the acute protective effects of coronary collaterals during coronary occlusion were closely associated with myocardial perfusion rather than the angiographic epicardial collateral vessel filling, and thus MCE was useful in assessing the acute protective effects of coronary collaterals during coronary occlusion.

Histologic correlates of angiographic chronic total coronary artery occlusions: influence of occlusion duration on neovascular channel patterns and intimal plaque composition

OBJECTIVES

Age-related changes in histologic composition and neovascular channel (NC) pattern of angiographic chronic total coronary artery occlusions (CTOs) were studied to define histologic correlates of age-related revascularization profiles and neovascular channel formation.

BACKGROUND

Revascularization of CTOs is frequently characterized by inability to cross or dilate the lesion and a high incidence of reocclusion or restenosis but low periprocedural ischemic complication rates. Little is known about the histopathologic basis of these observations.

METHODS

Ninety-six angiographic CTOs from autopsy studies in 61 patients who had undergone coronary angiography within 3 months of death were studied. Abrupt plaque rupture was excluded. Occlusion segments were analyzed for 1) histologic composition as a function of lesion age; and 2) NC pattern as a function of lesion age and intimal plaque (IP) composition.

RESULTS

Cholesterol and foam cell-laden IP was more frequent in younger lesions (p = 0.0007), whereas fibrocalcific IP increased with CTO age (p = 0.008). IP NCs arose directly from adventitial vasa vasorum and were anatomically and quantitatively related in terms of number and size (p = 0.0001) to the extent of IP cellular inflammation. IP cellular inflammation exceeded that found in the adventitia (p < 0.001) or media (p = 0.0001) across all CTO ages. In CTOs < 1 year old, the adventitia was associated with a larger number and size of NCs relative to the IP (p = 0.0006 and p = 0.009), media (p = 0.0001 and p = 0.002) and recanalized lumen (p = 0.0001 and p = 0.001). In CTOs >1 year old, the adventitia and IP NC numbers were similar and exceeded NC numbers found in the media (p = 0.0001) and recanalized lumen (p = 0.0001 and p = 0.003).

CONCLUSIONS

Angiographic CTO frequently corresponds to less than complete occlusion by histologic criteria. Age-related changes in IP composition from cholesterol laden to fibrocalcific may explain the adverse revascularization profile of older CTOs. IP NC growth derived from the adventitia increases with age and is strongly associated with IP cellular inflammation. IP NC formation may protect against the flow-limiting effects of IP growth.

Adaptation to myocardial ischemia during coronary angioplasty demonstrated by clinical, electrocardiographic, echocardiographic, and metabolic parameters

It has been shown that brief episodes of myocardial ischemia can render the heart more resistant to a prolonged subsequent ischemic episode. This phenomenon, called "preconditioning," has been described in human beings during coronary angioplasty with the use of clinical, electrocardiographic (ECG), or metabolic parameters. The goal of this study was to assess this phenomenon further with the use of echocardiographic and metabolic parameters in addition to clinical and ECG parameters. Eighteen patients with isolated stenosis of the left anterior descending coronary artery and a normal left ventricular function were included. Angioplasty consisted of four consecutive balloon inflations. Sequential changes in clinical, ECG (intracoronary ECG), echocardiographic, and metabolic parameters of myocardial ischemia were compared between the first and the fourth balloon inflations. Improved tolerance to myocardial ischemia with repeated coronary occlusions was demonstrated by a significant reduction in the severity of angina, ST-segment elevation, wall motion abnormalities, and lactate production. This study confirms the adaptation of myocardial ischemia to repeated coronary occlusions through measurement of clinical, ECG, echocardiographic, and metabolic parameters.

Clinical, angiographic and hemodynamic predictors of recruitable collateral flow assessed during balloon angioplasty coronary occlusion

OBJECTIVES

We sought to determine the predictive value of factors influencing coronary collateral vascular responses in humans.

BACKGROUND

There is limited information on the factors responsible for coronary collateral vascular development, despite the protective effect of collateral vessels in ischemic syndromes.

METHODS

Angiography of the contralateral artery was performed during balloon coronary occlusion in 105 patients with single-vessel disease (left anterior descending coronary artery in 69 patients, left circumflex coronary artery in 4 patients, right coronary artery in 32 patients) and normal left ventricular function. Collateral vessels were graded according to the classification of Rentrop. The relative collateral vascular resistance was calculated in a subgroup of 34 patients by means of aortic pressure, coronary wedge pressure and collateral flow, defined as the transient increase of coronary blood flow velocity of the contralateral artery during balloon coronary occlusion. Ischemia during coronary occlusion was evaluated by the ST segment shift (mV) in a 12-lead electrocardiogram (ECG).

RESULTS

A multivariate logistic analysis of clinical and angiographic variables revealed duration of angina (> or = 3 months, p < 0.0001), lesion severity (> or = 75% diameter stenosis, p < 0.0001) and proximal lesion location (p = 0.02) as independent factors positively associated with recruitability of collateral vessels, whereas the use of nitrates exerted an independent negative effect (p = 0.01). The regression equation yielded an overall predictive accuracy of 80%. The presence of recruitable collateral vessels during coronary occlusion resulted in a higher coronary wedge/aortic pressure ratio (mean [+/- SD] 0.35 +/- 0.13 vs. 0.27 +/- 0.12, p < 0.005), a lower relative collateral vascular resistance (6.7 +/- 7.4 vs. 21.3 +/- 10, p < 0.001) and a reduction of ECG signs of ischemia (0.14 +/- 0.19 vs. 0.38 +/- 0.33 mV, p < 0.001). The relative collateral vascular resistance was the best predictor for recruitability of collateral vessels compared with the other variables related to collateral vascular growth (p < 0.05).

CONCLUSIONS

Clinical and angiographic variables predict recruitability of collateral vessels with an 80% overall accuracy. These findings are important for risk stratification of patients undergoing interventions for ischemic coronary syndromes.

Differential characterization of human coronary collateral blood flow velocity

The functional importance and protective nature of the coronary collateral circulation has been well established. There are few data, however, regarding the phasic nature and absolute velocities of collateral flow in patients. The aim of this study was to characterize and quantify ipsilateral coronary collateral blood flow velocity in patients during coronary angioplasty. Coronary collateral flow velocity was measured in 49 patients during coronary angioplasty. Angiographic collateral filling was categorized by the Rentrop grading scale (0 to 3) and by anatomic pathway (epicardial, intramyocardial, or unknown [acutely recruited]). Collateral blood flow velocity was measured with a Doppler-tipped guide wire placed distal to the balloon occlusion in the collateralized vessel. Collateral flow velocity was characterized as predominantly systolic or diastolic, and phasic flow patterns were defined as biphasic (both systolic and diastolic), monophasic (only systolic or diastolic), or bidirectional (antegrade and retrograde velocity). Twenty-three (47%) patients had biphasic flow; 17 (35%) patients had monophasic flow; and 9 (18%) patients had bidirectional flow. Thirty-six (73%) of 49 patients had predominantly systolic flow signals. Epicardial collateral pathways had the highest total flow velocity integral, at 15.0 +/- 7.0 (vs intramyocardial [8.4 +/- 5.7] and acutely recruitable [5.4 +/- 2.1]; p < 0.05). There were no differences in flow velocity integrals among the Rentrop angiographic grades of collateral filling. These data establish three patterns of coronary collateral blood flow and demonstrate that the majority of collateral flow in the ipsllateral receiving vessel occurs during systole. The measurement of coronary collateral flow velocity provides a unique means to study the effects of pharmacologic or mechanical interventions on human collateral blood flow.