European Journal of Cardiovascular Medicine

Coronary heart diseases (CHD) have emerged as a major health burden worldwide with atherosclerosis being the prominent cause of death ^[1,2]. Three-fourths of deaths due to CHD occur in the low and middle income countries including India ^[3]. As prevention is better than cure, its early and apt diagnosis is important in risk stratification and for guiding further management.

 Previously, invasive diagnostic approaches were found to be used extensively, but the advancement in technology has now allowed non-invasive techniques to compete with the direct methods of diagnostics of coronary vascular pathology.

Due to the presence of an atherosclerotic plaque or in myocardial infarction, the coronary flow reserve (CFR) gets limited, which can be assessed by measuring coronary sinus flow using echocardiography.

The coronary sinus flow tends to be an indirect factor for evaluating the prognosis of MI with time. Earlier, transesophageal echocardiography (TEE) was mostly used for measurements of CFR in the proximal significant left descending artery (LAD) stenosis ^{[4, 5]}. However, TEE fails to measure the mid and distal segments of the coronary tree due to its non-visualization.

As 95% of the left ventricular perfusion drains into the right atrium through the coronary sinus, the flow in this vessel is a good representation of the global left ventricular perfusion. A recent study demonstrates that reduced ante grade flow in the coronary sinus detected by transthoracic Doppler echocardiography is a sensitive predictor of coronary artery stenosis. TTE assessment of CFR in the distal LAD and right coronary artery (RCA) is significantly correlated with the results obtained with intracoronary Doppler wire for the LAD and RCA stenosis ^{[6, 7]}.

This Single centered, pre-post interventional study was conducted in Cardiology Department of Jawaharlal Nehru Medical College, KAHER, Belagavi.  The study is being conducted from January 2023 to June 2024 

Sample size:

Size of the effect that is clinically worthwhile to detect (d)= 0.9

         The probability of falsely rejecting a true null hypothesis (α)=0.05

       The probability of failing to reject a false null hypothesis (β)= 0.80

       Standard deviation of population being studied (SD)= 3.22

N= (1.96 + 0.84)2 x (3.22) 2   / (0.9) 2

      = 100

      Total sample need for the study is 100.

      Sample size taken is 150.

By using this equation, a sample size of 150 was obtained.

Sampling method: Purposive sampling method

Inclusion Criteria

• Patients admitted to cardiology department of KLE hospital with ACS. ACS diagnosed according to the fourth universal definition of acute myocardial infarction. Thrombolysed or not thrombolysed.

Exclusion criteria

Patients with poor echo window.

Hemodynamic instability.

Mitral or tricuspid valve regurgitation of a grade more than 2+.

Patients who are contraindicated for coronary angiography.

Persons with cardiac risk factors or previous CVS disorders were excluded from the study.

Patient refused consent to be part of study

Methodology

All patients fulfilling the inclusion criteria and willing to participate in the study by signing the informed consent were included in the study.

 A detailed information on demographics, patient history and physical examination were collected in a case proforma designed specifically for the study.

Blood was drawn at admission for biochemical analysis. This included CBC, renal function test, Troponin I and HbA1c.

Heart rate and Bloop pressure were recorded at admission. 12 lead Electrocardiogram (ECG) and 2D Echocardiography were also done at admission. Standard coronary angiogram was performed in all patients with at least two views of the right coronary artery and four views of the left coronary artery.

Investigations including

• Glycated Hemoglobin levels (HbA1c; < 5.7 normal , 5.7 -6.4 % prediabetes , ³ 6.5 diabetes mellitus )
• Troponin I ( >0.01 ng/ml abnormal )
• Serum creatinine levels (normal: Females, 0.60-0.90 mg/dL; Males, 0.70- 1.20 mg/dL)
• Complete blood count

12 lead Electrocardiogram was done using Nihon kohdencardiofax M machine and 2D-Echocardiogram was done using Philips CX 50 portable echo machine (Serial number: BOYKSR) within 6 hours of admission

• Echocardiogram parameters:
• M-Mode: left ventricular end diastolic diameter:
  • left ventricular end-systolic diameter:
  • left ventricular Ejection fraction:
• Coronary sinus diameter(cm):
• Peak velocities (centimeters per second):
• Peak pressure gradient (millimeters of mercury):
• Mean velocities (centimeters per second):
• Mean pressure gradient (millimeters of mercury):
• Velocity-time integral (centimeters) :
• Coronary Blood flow per stroke = π × D2/4 × velocity time integral =
• Coronary Blood flow per minute = π × D2/4 × velocity-time integral × heart rate =

Images were obtained using standard echocardiographic equipment utilizing a transducer with frequency range of 1.7–3.4 MHz. Blood pressure and heart rate were obtained at time of echocardiography. A modified parasternal right ventricular inflow view was obtained to visualize the coronary sinus by two-dimensional echocardiography. Then color Doppler imaging was used to identify the CSBF. A pulsed wave Doppler sample was placed 0.5–1 cm into the ostium of the coronary sinus, with angle of incidence of less than 60°. A CSBF velocity envelope was identified by a characteristic pattern consisting of 3 components: forward systolic flow, forward diastolic flow and retrograde diastolic flow, the latter corresponding to atrial contraction. A time–velocity integral was calculated by tracing the velocity profile for each flow component separately. Measurements were made in three consecutive beats, and the average was used for subsequent analysis.

• A modified apical 4-chamber view with the transducer tilted posteriorly was used to visualize the coronary sinus. M-mode echocardiograms were obtained to measure the coronary sinus diameter between 0.5 and 1 cm from the opening of the coronary sinus into the right atrium. Systolic and diastolic measurements were obtained.
• Using these measurements, CSBF was calculated as the product of coronary sinus cross-sectional area, the antegrade CSBF time–velocity integrals, and the heart rate, as follows:

                       CSBF = 𝜋× D2∕4 × (VTIcs) × HR

  where CSBF = coronary sinus blood flow (mL/min), D = CS diameter in diastole (cm), VTIcs= CSBF time–velocity integral (cm) and HR = heart rate (bpm).

Table 1 Demographic and Clinical Characteristics of Patients Undergoing Coronary Artery Intervention

The demographic and clinical characteristics of the patient population reveal a predominance of male patients, accounting for 66% of the total, while females represent 34%. The vast majority of patients (87.33%) presented with chest pain, and 60.67% did not experience dyspnea, leaving 39.33% who did. Syncope was a rare symptom, reported by only 1.33% of the patients. Most patients did not report palpitations (96%) or angina equivalents (97.33%), with a small percentage experiencing giddiness or sweating (1.33% each).

Hypertension was prevalent in the population, with 52.67% of patients having the condition, and 40.67% were diabetic. Chronic kidney disease (CKD) was uncommon, with 96.67% of patients not having it, and a very small number (2%) were diagnosed with CKD, including 1.33% with polycystic kidney disease (PCKD). Chronic obstructive pulmonary disease (COPD) was also rare, affecting only 4% of the patients.

Regarding lifestyle factors, 20.67% of the patients were smokers, 34.67% used tobacco, and 20% consumed alcohol. The majority of patients were classified as Killip class I (62%), followed by class II (35.33%), with a very small percentage in class III (2.67%).

In terms of clinical categories, NSTEMI was the most common diagnosis (40.67%), followed by unstable angina (32.67%). STEMI-AWMI accounted for 16% of cases, while other types of STEMI were less common. Coronary angiography (CAG) findings showed that 55.33% of patients had single-vessel disease (SVD), 30% had double-vessel disease (DVD), and 14.67% had triple-vessel disease (TVD).

The patient population reveal a predominance of male patients, accounting for 66% of the total, while females represent 34%.

The vast majority of patients (87.33%) presented with chest pain

The majority of patients were classified as Killip class I (62%), followed by class II (35.33%), with a very small percentage in class III (2.67%).

Coronary angiography (CAG) findings showed that 55.33% of patients had single-vessel disease (SVD), 30% had double-vessel disease (DVD), and 14.67% had triple-vessel disease (TVD).

The majority of 59.3% patients were not diabetes whereas, 40.67% were diabetic

Hypertension was prevalent in the population, with 52.67% of patients having the condition

Table 2 Descriptive Statistics of Clinical Parameters in Patients Undergoing Cardiac Intervention

The patient population has a mean age of 60 years with a standard deviation of 11.29 years. The average Body Mass Index (BMI) is 27.61, suggesting that the population is, on average, slightly overweight, with a standard deviation of 4.68. Blood pressure (BP) readings show a mean of 109.64 mmHg with a standard deviation of 12.78 mmHg.The mean pulse rate is 76.43 beats per minute, with a standard deviation of 13.6, indicating a relatively normal heart rate for this population. The ejection fraction, which is a measure of the heart's pumping efficiency, has a mean of 49.90 and standard deviation of 9.0. The average diameter of the coronary sinus (CS) is 0.85 cm, with a standard deviation of 0.2 cm. Coronary Sinus Blood Flow (CSBF) per beat has a mean of 3.03 mL, with a standard deviation of 1.52 ml. On admission, the mean CSBF per minute is 218.63 mL, with a standard deviation of 93.64 ml. After Percutaneous Coronary Intervention (PCI), the mean CSBF significantly increases to 372.05 mL per minute, with a standard deviation of 126.15 ml, reflecting the effectiveness of PCI in improving coronary blood flow in this patient group.

Table 3 Coronary Sinus Blood Flow (CSBF) on Admission and Post-Percutaneous Coronary Intervention (PCI) by Patient Characteristics

Males had higher CSBF both on admission (226.52 ± 98.5 mL/min) and post-PCI (382.54 ± 129.92 mL/min). This suggests that males experienced slightly greater increases in CSBF following PCI. Patients presenting with chest pain had slightly higher CSBF on admission (220.15 ± 95.99 mL/min) and post-PCI (375.43 ± 128.43 mL/min). Patients with dyspnea had higher CSBF on admission (223.77 ± 92.08 mL/min) and post-PCI (377.45 ± 116.8 mL/min). Patients without palpitations had slightly higher CSBF on admission (219.31 ± 92.7 mL/min) but a lower increase post-PCI (371.48 ± 124.64 mL/min) compared to those with palpitations, whose CSBF increased from 202.38 ± 123.37 mL/min to 385.65 ± 172.13 mL/min post-PCI. Patients without angina equivalents had higher CSBF on admission (220.29 ± 92.84 mL/min) and post-PCI (375.19 ± 123.78 mL/min). Patients with hypertension showed a slight increase in CSBF on admission (222.78 ± 94.26 mL/min) and post-PCI (370.04 ± 130.05 mL/min) compared to those without hypertension. Diabetic patients had a higher CSBF on admission (238.71 ± 92.76 mL/min) and post-PCI (397.36 ± 128.36 mL/min) compared to non-diabetic patients. Patients with CKD had higher CSBF on admission (246.15 ± 81.85 mL/min) compared to those without CKD, with a slight increase post-PCI (373.53 ± 144.31 mL/min). Smokers and tobacco users had slightly higher CSBF on admission and post-PCI compared to non-smokers and non-tobacco users, indicating a potential impact of smoking on coronary blood flow. Patients who consumed alcohol had slightly higher CSBF on admission and post-PCI compared to non-drinkers, suggesting alcohol might influence coronary blood flow. Patients in Killip Class III had the highest CSBF on admission (276.23 ± 87.83 mL/min) and the most significant increase post-PCI (393.88 ± 78.57 mL/min), indicating more severe initial cardiac compromise and a greater response to PCI compared to those in Killip Classes I and II. Overall, the data shows that PCI leads to significant increases in CSBF across all patient subgroups, with variations observed based on demographic and clinical characteristics. These findings underscore the importance of personalized approaches to managing coronary artery disease.

Table 4 Comparative Analysis of Coronary Sinus Blood Flow (CSBF) on Admission and Post-Percutaneous Coronary Intervention (PCI)

*significance is obtained by paired t test

The data compares Coronary Sinus Blood Flow (CSBF) in 150 patients measured on admission and after undergoing Percutaneous Coronary Intervention (PCI). On admission, the mean CSBF was 218.88 mL/min with a standard deviation of 93.90 mL/min, indicating significant variability in baseline coronary blood flow among the patients. Following PCI, the mean CSBF significantly increased to 372.05 mL/min with a standard deviation of 126.15 mL/min. The t-test result of -21.88, with a p-value less than 0.05, indicates that this increase in CSBF post-PCI is statistically significant. This substantial improvement in coronary blood flow highlights the effectiveness of PCI in enhancing coronary perfusion in this patient population.

Table 5 Coronary Sinus Blood Flow (CSBF) on Admission and Post-Percutaneous Coronary Intervention (PCI) Across Different Clinical Categories

*significance is obtained by paired t test

The data presents the changes in Coronary Sinus Blood Flow (CSBF) on admission and after Percutaneous Coronary Intervention (PCI) across different clinical categories. For patients with NSTEMI, the mean CSBF increased from 212.74 ± 103.65 mL/min on admission to 360.03 ± 129.91 mL/min post-PCI, with a t-value of -5.042, indicating a statistically significant improvement (p < 0.05).

In patients with STEMI-AWMI, the mean CSBF showed a substantial increase from 226.23 ± 82.63 mL/min on admission to 430.61 ± 118.99 mL/min post-PCI. This change was highly significant, with a t-value of -12.860 (p < 0.05), reflecting the pronounced benefit of PCI in this group. For patients with STEMI-IWMI, the mean CSBF rose from 207.88 ± 92.62 mL/min on admission to 343.5 ± 121.21 mL/min after PCI, with a t-value of -5.630, also indicating a statistically significant improvement (p < 0.05). Similarly, in patients with Unstable Angina (USA), the mean CSBF increased from 224.95 ± 87.97 mL/min on admission to 367.17 ± 122.2 mL/min post-PCI, with a t-value of -11.762, showing a significant positive impact of PCI (p < 0.05).

Overall, these results demonstrate that PCI significantly improves coronary blood flow in patients across all these categories, with the most substantial increases observed in those with STEMI-AWMI. These findings highlight the critical role of PCI in enhancing coronary perfusion and improving outcomes in patients with various types of myocardial infarction and unstable angina.

Table 6 Coronary Artery Disease Severity on Coronary Sinus Blood Flow (CSBF) Pre- and Post-Percutaneous Coronary Intervention (PCI)

*significance is obtained by paired t test

The data compares Coronary Sinus Blood Flow (CSBF) before and after Percutaneous Coronary Intervention (PCI) in patients categorized by the severity of their coronary artery disease, as determined by Coronary Angiography (CAG). For patients with Double Vessel Disease (DVD), the mean CSBF on admission was 197.88 ± 82.04 mL/min, which significantly increased to 342.15 ± 119.01 mL/min after PCI. The t-value of -12.269 and a p-value less than 0.05 indicate that this improvement is statistically significant. In those with Single Vessel Disease (SVD), the mean CSBF increased from 221.3 ± 95.82 mL/min on admission to 375.67 ± 122.72 mL/min post-PCI. The t-value of -15.824 with a p-value less than 0.05 confirms that this increase is also statistically significant, highlighting the effectiveness of PCI in patients with less extensive coronary artery disease. For patients with Triple Vessel Disease (TVD), who had more severe coronary artery disease, the mean CSBF rose from 250.99 ± 101.06 mL/min on admission to 413.65 ± 143.88 mL/min after PCI. Despite the severity of their condition, this group also experienced a significant improvement in CSBF, as indicated by the t-value of -8.689 and a p-value less than 0.05.

Overall, these findings demonstrate that PCI is effective in significantly improving coronary blood flow across all levels of coronary artery disease severity, with the most substantial increases observed in patients with TVD. This underscores the importance of PCI in managing patients with varying degrees of coronary artery involvement.

Table 7 Coronary Sinus Blood Flow (CSBF) Before and After Thrombolysis in Different Types of Myocardial Infarction (MI)

*significance is obtained by paired t test

The data presented provides an analysis of coronary sinus blood flow (CSBF) in patients with STEMI-AWMI (anterior wall myocardial infarction) and STEMI-IWMI (inferior wall myocardial infarction) across different treatment stages. For patients with STEMI-AWMI, the CSBF on admission averaged 226.23 mL/min, which significantly increased to 357.85 mL/min after thrombolysis (indicated by a significant t-value of -8.743). Post-percutaneous coronary intervention (PCI), the CSBF further improved to an average of 430.61 mL/min, with a more pronounced t-value of -12.860, indicating a significant enhancement in blood flow post-treatment.

Similarly, for patients with STEMI-IWMI, the CSBF on admission was lower, averaging 207.88 mL/min. Following thrombolysis, the CSBF increased to 287.23 mL/min, with a significant t-value of -5.914. After PCI, the CSBF further rose to 343.5 mL/min, with a t-value of -5.630, reflecting a statistically significant improvement.

In both groups, the data highlights a significant increase in coronary blood flow following thrombolysis and further enhancement after PCI, underscoring the effectiveness of these interventions in restoring coronary perfusion in STEMI patients002E.

In the current study, most of the patients were males. The patient population has a mean age of 60 years with a standard deviation of 11.29 years. The average Body Mass Index (BMI) is 27.61, suggesting that the population is, on average, slightly overweight, with a standard deviation of 4.68.

Samir et al ²⁷- did a study on 492 STEMI patients. Young STEMI patients constituted for 20%  of all STEMI cases. Male gender was predominantly seen, similar to the current study.

In the study done by Kim MK et al ²⁸ mean age of patients with SMI was 63.1 years.

In DIAD STUDY, ²⁹ authors found age of patients with SMI ranges from 61 to 64years.  Males had more incidence of SMI due to large perfusion abnormality compared to females. Chest pain is the most common complaint followed by dyspnea and syncope in the current study. Hypertension was prevalent in the population, followed by diabetes. condition, and 40.67% were diabetic. Chronic kidney disease and PCKD were seen rarely in the current study

Nicotine dependence can also aggravate blood vessel degeneration and cause inflammatory response, enhances oxidative stress for NADPH oxidase-1, accelerating arteriosclerosis, which can lead to STEMI.

Diagnosis:

NSTEMI was the most common diagnosis (40.67%), followed by unstable angina (32.67%). STEMI-AWMI accounted for 16% of cases, while other types of STEMI were less common. Coronary angiography (CAG) findings showed that 55.33% of patients had single-vessel disease (SVD), 30% had double-vessel disease (DVD), and 14.67% had triple-vessel disease (TVD).

Coronary angiography (CAG) findings showed that 55.33% of patients had single-vessel disease (SVD), 30% had double-vessel disease (DVD), and 14.67% had triple-vessel disease (TVD).

Ejection fraction and CSF:

The ejection fraction, which is a measure of the heart's pumping efficiency, has a mean of 29.74% and a large standard deviation of 26.06%, suggesting significant variability and indicating that many patients may have reduced cardiac function.

The average diameter of the coronary sinus (CS) is 0.85 cm, with a standard deviation of 0.2 cm. Coronary Sinus Blood Flow (CSBF) per beat has a mean of 3.03 mL, with a standard deviation of 1.52 ml. On admission, the mean CSBF per minute is 218.63 mL, with a standard deviation of 93.64 mL. After Percutaneous Coronary Intervention (PCI), the mean CSBF significantly increases to 372.05 mL per minute, with a standard deviation of 126.15 ml, reflecting the effectiveness of PCI in improving coronary blood flow in this patient group.

Males had higher CSBF both on admission (226.52 ± 98.5 mL/min) and post-PCI (382.54 ± 129.92 mL/min). This suggests that males experienced slightly greater increases in CSBF following PCI. Patients presenting with chest pain had slightly higher CSBF on admission (220.15 ± 95.99 mL/min) and post-PCI (375.43 ± 128.43 mL/min). Patients with dyspnea had higher CSBF on admission (223.77 ± 92.08 mL/min) and post-PCI (377.45 ± 116.8 mL/min).

Patients with CKD had higher CSBF on admission (246.15 ± 81.85 mL/min) compared to those without CKD, with a slight increase post-PCI (373.53 ± 144.31 mL/min). Smokers and tobacco users had slightly higher CSBF on admission and post-PCI compared to non-smokers and non-tobacco users, indicating a potential impact of smoking on coronary blood flow. Overall, the data shows that PCI leads to significant increases in CSBF across all patient subgroups, with variations observed based on demographic and clinical characteristics. These findings underscore the importance of personalized approaches to managing coronary artery disease in the current study,

CSBF after PCI:

On admission, the mean CSBF was 218.88 mL/min with a standard deviation of 93.90 mL/min, indicating significant variability in baseline coronary blood flow among the patients. Following PCI, the mean CSBF significantly increased to 372.05 mL/min with a standard deviation of 126.15 mL/min. The t-test result of -21.88, with a p-value less than 0.05, indicates that this increase in CSBF post-PCI is statistically significant. This substantial improvement in coronary blood flow highlights the effectiveness of PCI in enhancing coronary perfusion in this patient population.

In patients with STEMI-AWMI, the mean CSBF showed a substantial increase from 226.23 ± 82.63 mL/min on admission to 430.61 ± 118.99 mL/min post-PCI. This change was highly significant, with a t-value of -12.860 (p < 0.05), reflecting the pronounced benefit of PCI in this group. For patients with STEMI-IWMI, the mean CSBF rose from 207.88 ± 92.62 mL/min on admission to 343.5 ± 121.21 mL/min after PCI, with a t-value of -5.630, also indicating a statistically significant improvement (p < 0.05). Similarly, in patients with Unstable Angina (USA), the mean CSBF increased from 224.95 ± 87.97 mL/min on admission to 367.17 ± 122.2 mL/min post-PCI, with a t-value of -11.762, showing a significant positive impact of PCI (p < 0.05).

Overall, these results demonstrate that PCI significantly improves coronary blood flow in patients across all these categories, with the most substantial increases observed in those with STEMI-AWMI in the current study.

• Mean CSBF values were significantly lower in NSTEMI and STEMI patients than in those with USA.
• Among patients with AMI who underwent thrombolysis, patients with AWMI had greater percentage increase in CSBF levels after thrombolysis than patients with IWMI
• Patients with AWMI who had initially lower CSBF values, had a greater percentage increase after PCI than patients with higher initial values
• Also patients with AWMI with lower CSBF values had higher incidence of DVD or TVD .
• This study extend prior observations that CSBF represents an attractive physiologic measure of total coronary perfusion. Completely non-invasive assessment of CSBF with transthoracic echocardiography provides an objective estimation of the improvement in myocardial perfusion
• It is conceivable that the degree of change in CSBF after revascularization could provide prognostic information regarding the likelihood of freedom from angina, recurrent cardiovascular events, or improvement in left ventricular function. Additionally, repeated measurements of CSBF may help to gauge longitudinal changes in coronary perfusion, including efficacy of revascularization, stent patency or development of new obstructive lesions.
• For medically managed patients with CAD, obtaining a baseline CSBF and reassessing this physiologic parameter after changes in treatment (e.g., with vasodilators) may provide an objective measure to assess the effect of these changes

BedrudinBanjanovicet al. studied the Non Invasive Detection of Coronary Sinus Flow Changes Over Time After CABG. ⁸

The formation of new blood in the vascular bed after CABG may represent ischemia and a change in normal nutrition. Its quantification helps to better understand coronary hemodynamics after revascularization.

61 patients were included in their study and TTE recordings measured CS flow before and two times after CABG.

The parameters that were measured are

- CS diameter

- Velocity Time Integral

-systemic hemodynamic data

- LV mass calculation

The results were as follows:

- low overall CS flow was found preoperatively

- After surgery, an increase of CS flow was noted

Their study concluded that there was a significantly new amount of blood in coronary bed after CABG, with constant increase in the postoperative period.

Sukhjinder S. Nijjer et al.⁹ Evaluated changes in blood flow after PCI in relation to systemic disease outcomes from the JUSTIFY-PCI trial. Their study evaluated changes in resting and hyperemic flow velocities after PCI in physiologically stenosed areas. 67 patients were included in their study and the parameter measured was Flow velocity over the whole cardiac cycle and the wave-free period.  The results were as follows:  Hyperemic flow velocities are reduced in physiologically significant stenosis before PCIThere is no difference between resting flow velocities and hyperemic flow velocities in significant stenoses.

Relaxation time increased after PCI and was lower than hyperemic flow.

The greatest increase in hyperemic flow was observed during stenosis treatment

Their study concluded that Pre-PCI physiology is strongly associated with post-PCI increase in hyperemic coronary flow velocity.

Daniel Wing Chong Ng et al. investigated the value of TTE in imaging arteries after coronary artery bypass grafting. In their study, 15 patients were included and the coronary sinus blood flow was measured using transthoracic echocardiography before and after coronary artery bypass surgery in 15 patients. Coronary sinus blood flow revascularization was increased after the procedure and this finding is similar to that seen in previous interventional procedures.¹⁰

P S Nagaraja et al.estimated coronary sinus blood flow for the adequacy of revascularization in subjects undergoing off pump coronary artery bypass graft using Transesophageal echocardiography.¹¹ Their study evaluated CSBF before and after each branch of the left coronary artery to determine the adequacy of surgical revascularization in patients selected to undergo coronary artery bypass grafting using TEE. Thirty patients were included in their study and the following parameters were measured. CSBF before and after each branch of LCA revascularization using TEE.  Left internal mammary artery (LIMA) Doppler obtained post LIMA to left anterior descending (LAD) grafting. The results were as follows: The CSBF per beat, CSBF per minute and total velocity time integral before LAD grafting showed significant increase to values after LAD revascularization. The CSBF per beat, CSBF per minute and total VTI before obtuse marginal grafting showed statistically significant increase to values after OM revascularization. In nine patients, color flow Doppler of LIMA was demonstrated which showed diastolic predominant blood flow after LIMA to LAD grafting.

Their study concluded that demonstration of CSBF is straightforward and that monitoring trends in CSBF values before and after each change in LCA area will guide the decision of adequacy of revascularization.

RadmilaLyubarova et al. did a study that concluded that Successful PCI improves coronary sinus blood flow as assessed by transthoracic echocardiography¹²

Their study included 31 patients and the parameters measured were

• CSBF per cardiac cycle measured using transthoracic two-dimensional
• Doppler flow imaging
• CSBF was assessed before and after cardiac catheterization

The results were as follows: In patients who did not undergo PCI, there was no change in CSBF. In patients who underwent PCI, CSBF increase was noted.

Other hemodynamic and echocardiographic parameters did not change before and after cardiac catheterization in either treatment group. Their study concluded that TEE assessment is useful to document CSBF changes after angioplasty.

H Lambertz et al. conducted a study on the Noninvasive determination of coronary flow reserve with high resolution transthoracic Doppler color echocardiography.¹³
Their study evaluated the feasibility of assessing the coronary flow reserve in the LAD, noninvasively, through echo-enhanced high-resolution transthoracic color Doppler echocardiography (TTCD), using cardiac catheterization measurements of coronary diameter stenosis as a reference. 45 patients were included in their study and were divided into: Group I - 15 patients without heart disease,  Group II - 15 patients with 40 to 70% isolated LAD diameter stenosis,  Group III - 15 patients with > 70% LAD diameter stenosis. Peripheral LAD coronary flow at baseline condition was assessed in 40 patients using TTCD.  The results were as follows: CFR in Group I was highest. CFR in Group III was lowest. Their study concluded that CFR of LAD can be determined by the synergistic use of high-resolution TTCD combined with intravenous given ultrasound echo-enhancing agent.

I V Bogatyrev et al. did a study on Coronary venous blood flow in patients with acute myocardial infarction. Their study included 94 patients with large myocardial infarction and the parameter assessed was  coronary venous blood flow by continuous coronary sinus thermodilution.  The results were as follows:- In patients with anterior MI less blood flow in the vena cordis magna was noted compared to other group.  No relation was found between the blood flow and precordial parameters. No relationship was noted between the coronary venous blood flow and the duration of heart disease.

Their study concluded that the coronary sinus thermodilution cannot be used for indirect identification of the site of MI and for prediction of its progression severity.¹⁴

Prajapati, Mrugeshet al.(2021) ¹⁵ did a study on the measurement of coronary sinus blood flow using TEE to estimate the revascularization in patients undergoing off-pump coronary artery bypass grafting. 100 patients were included in their study.

The following parameters were calculated

- velocity time integral of CS

- coronary sinus diameter

- coronary sinus cross-section area

-coronary sinus blood flow per beat and minute.

The results were as follows: Significant increase in velocity time integral in the post-revascularization period. There was increase in mean CS diameter in the post-revascularization period. Increase in CSBF per minute in the post-revascularization period. Their study concluded that TEE is a superior modality to evaluate CSBF before and after coronary artery bypass revascularization. 

Non-invasive evaluation of CSBF using transthoracic echocardiography is technically feasible in all patients undergoing PCI. It is a potentially simple, repeatable, cost-effective, non-cumbersome imaging modality for the assessment of CSBF in patients with CAD, and especially for those with AWMI. It can also be used to assess the effectiveness of treatment in patients with CAD. Results reflect hemodynamically significant changes in total coronary blood flow. Echocardiography may be to serve as a proxy of revascularization success, no reflow phenomenon and longitudinal gauging of coronary blood flow. Further studies are required to see if serial measurements could correlate with clinical events.

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