Transthoracic Doppler echocardiographic analysis of phasic coronary blood flow velocity in hypertrophic cardiomyopathy

Hypertrophic Cardiomyopathy-Septal Perforator Arteries Doppler Flow Dynamics

BACKGROUND

Patients with hypertrophic cardiomyopathy (HCM) have been shown to exhibit abnormal diastolic vessel flow; however, flow pattern profiles and their possible association with different grades of diastolic dysfunction have not been studied. Color Doppler two-dimensional echocardiography permits visualization of the septal perforator arteries, and pulsed-wave Doppler allows recording of diastolic septal artery flow (SAF). Through routine visualization of the septal perforator arteries and acquisition of SAF, we noticed 3 patterns of SAF in patients with HCM. In this study, we aimed to assess the feasibility of the acquisition of SAF and to describe types of SAF in an HCM cohort and their associations with diastolic function.

METHODS

We reviewed two-dimensional echocardiograms and the electronic records of 108 patients with HCM in whom septal artery color and spectral Doppler had been performed. The peak diastolic and end-diastolic velocities, diastolic slope, diastolic flow time-velocity integral, and systolic flow reversal of the septal perforator arteries were recorded with pulsed-wave Doppler. Echocardiographic and clinical characteristics were analyzed.

RESULTS

A reproducible pulsed-wave Doppler tracing was recorded in 54% of patients with HCM. Three distinct patterns of SAF were identified: type 1-smooth, linear holodiastolic velocity decrease; type 2-with presence of an atrial dip; and type 3-biphasic velocity decrease with an early, rapid diastolic slope and a mid-to-late gentle slope. These 3 SAFs correlated with different grades of diastolic dysfunction.

CONCLUSION

Septal artery flow could be detected in more than 50% of patients with HCM. Three distinct types of SAF were identified, correlating with different grades of diastolic dysfunction. These 3 types of SAF can provide additional information about left ventricular end-diastolic pressure and diastolic function in patients with HCM in whom diastolic function may be difficult to determine.

Myocardial perfusion and function dichotomy in growth restricted preterm infants

Compared to preterm appropriate for gestational age (AGA) fetuses, fetuses with fetal growth restriction (FGR) have earlier visualisation of coronary artery blood flow (CABF) but impaired cardiac function. This dichotomy remains uncharacterised during postnatal life. This study compared CABF and cardiac function in preterm FGR infants, against AGA infants during the postnatal period. FGR was defined as birthweight < 10^th centile for gestation and sex with absent/reversed antenatal umbilical artery Doppler. Diastolic CABF was measured in the left anterior descending coronary artery. Twenty-eight FGR infants were compared with 26 AGA infants (gestation and birthweight, 29.7 ± 1.3 vs 29.9 ± 1 weeks, P = 0.6 and 918 ± 174 vs 1398 ± 263g, P < 0.001, respectively). Echocardiography was performed in the second week of life. FGR infants had higher CABF (velocity time integral, 2.4 ± 0.9 vs 1.6 ± 0.8 cm, P = 0.002). Diastolic function was impaired (↑ trans-mitral E/A ratio in FGR infants; 0.84 ± 0.05 vs 0.79 ± 0.03, P = 0.0002) while the systolic function was also affected (mean velocity of circumferential fibre shortening [mVCFc], 1.9 ± 0.3 vs 2.7 ± 0.5 circ/s, P < 0.001). Indexing CABF to cardiac function noted significant differences between the groups (CABF: E/A [FGR vs AGA], 2.9 ± 1.1 vs 2.1 ± 1, P = 0.01 and CABF: mVCFc [FGR vs AGA], 1.3 ± 0.5 vs 0.6 ± 0.3, P < 0.001). Diastolic blood pressure (BP) was significantly higher, and CABF to diastolic BP ratio trended higher in FGR infants (30 ± 2 vs 25 ± 3 mmHg, P < 0.001 and 0.08 ± 0.03 vs 0.06 ± 0.03, P = 0.059, respectively). Greater CABF in FGR infants did not translate into better cardiac function. This dichotomy may be a persistent response to fetal hypoxaemia (fetal programming) and/or reflection of altered cardiac architecture.

Phasic flow patterns of right versus left coronary arteries in patients undergoing clinical physiological assessment

BACKGROUND

Coronary blood flow in humans is known to be predominantly diastolic. Small studies in animals and humans suggest that this is less pronounced or even reversed in the right coronary artery (RCA).

AIMS

This study aimed to characterise the phasic patterns of coronary flow in the left versus right coronary arteries of patients undergoing invasive physiological assessment.

METHODS

We analysed data from the Iberian-Dutch-English Collaborators (IDEAL) study. A total of 482 simultaneous pressure and flow measurements from 301 patients were included in our analysis.

RESULTS

On average, coronary flow was higher in diastole both at rest and during hyperaemia in both the RCA and LCA (mean diastolic-to-systolic velocity ratio [DSVR] was, respectively, 1.85±0.70, 1.76±0.58, 1.53±0.34 and 1.58±0.43 for LCArest, LCAhyp, RCArest and RCAhyp, p<0.001 for between-vessel comparisons). Although the type of RCA dominance affected the DSVR magnitude (RCAdom=1.55±0.35, RCAco-dom=1.40±0.27, RCAnon-dom=1.35; standard deviation not reported as n=3), systolic flow was very rarely predominant (DSVR was greater than or equal to 1.00 in 472/482 cases [97.9%] overall), with equal prevalence in the LCA. Stenosis severity or microvascular dysfunction had a negligible impact on DSVR in both the RCA and LCA (DSVR x hyperaemic stenosis resistance R2 =0.018, p=0.03 and DSVR x coronary flow reserve R2 <0.001, p=0.98).

CONCLUSIONS

In patients with coronary artery disease undergoing physiological assessment, diastolic flow predominance is seen in both left and right coronary arteries. Clinical interpretation of coronary physiological data should therefore not differ between the left and the right coronary systems.

Regional difference of microcirculation in patients with asymmetric hypertrophic cardiomyopathy: transthoracic Doppler coronary flow velocity reserve analysis

OBJECTIVE

To evaluate, by noninvasive coronary flow velocity reserve (CFVR), whether patients with asymmetric hypertrophic cardiomyopathy (HC), with or without left ventricular outflow tract obstruction, demonstrate significant regional differences of CFVR.

METHODS

We evaluated 61 patients with HC (27 men; mean age 49 ± 16 years), including 20 patients with hypertrophic obstructive cardiomyopathy (HOCM) and 41 patients without obstruction (HCM). The control group included 20 age- and sex-matched subjects. Transthoracic Doppler echocardiography CFVR of the left anterior descending coronary artery (LAD) and the posterior descending coronary artery (PD) were performed, including calculation of relative CFVR as the ratio between CFVR LAD and CFVR PD.

RESULTS

Compared with the controls, all the patients with HC had lower CFVR LAD (2.12 ± 0.53 vs 3.34 ± 0.67; P < .001) and CFVR PD (2.29 ± 0.49 vs 3.21 ± 0.65; P < .001). CFVR LAD in HOCM group in comparison with the HCM group was significantly lower (1.93 ± 0.42 vs 2.22 ± 0.55; P = .047), due to higher basal diastolic coronary flow velocities (0.40 ± 0.09 vs 0.33 ± 0.07 m/sec; P = .002), with similar hyperemic diastolic flow velocities (0.71 ± 0.16 vs 0.76 ± 0.19 m/sec; P = .330), respectively. There was no significant difference in CFVR PD between patients with HOCM and those with HCM (2.33 ± 0.46 vs 2.27 ± 0.50; P = .636), respectively. Relative CFVR was lower in the HOCM group compared with the HCM group (0.84 ± 0.16 vs 0.98 ± 0.14; P = .001). By multivariable regression analysis, left ventricular outflow tract gradient was the independent predictor of CFVR LAD (B = -0.24; P = .008) and relative CFVR (B = -0.34; P = .016).

CONCLUSIONS

CFVR LAD and relative CFVR were significantly lower in patients with HOCM compared with patients with HCM. Regional differences of CFVR are present only in patients with significant left ventricular outflow tract obstruction, which suggests that obstruction per se, by increasing wall stress in basal conditions, leads to higher basal diastolic coronary flow velocities and results in lower CFVR in LAD compared with PD.

Diastolic flow velocity pattern of the left anterior descending coronary artery in hypertrophied heart, with special reference to the difference between hypertrophic cardiomyopathy and hypertensive left ventricular hypertrophy

BACKGROUND

This study aimed to clarify the characteristics of diastolic flow velocity pattern of the left anterior descending coronary artery (LAD) in patients with left ventricular hypertrophy (LVH), and the difference in diastolic LAD flow velocity pattern between hypertensive LVH and hypertrophic cardiomyopathy (HCM).

METHODS

The flow velocity pattern was recorded at the mid-portion of the LAD by high-frequency transthoracic Doppler echocardiography in 22 patients with HCM, 10 hypertensive patients with LVH [LVH(+)HT], and 9 hypertensive patients without LVH [LVH(-)HT]. The diastolic flow pattern was analyzed. Standard two-dimensional echocardiogram and apexcardiogram (ACG) were also recorded.

RESULTS

The interventricular septal thickness (IVST) and the sum of the IVST and LV posterior wall thickness (PWT) (IVST + PWT) were greater in HCM than in HT (p < 0.01) patients. Early diastolic upstroke time (D-UT) of the LAD flow velocity wave was longest in HCM, and was longer in LVH(+)HT than in LVH(-)HT (p < 0.01) patients. Direct correlation was found between D-UT and IVST, IVST + PWT in patients with LVH(+)HT and LVH(-)HT (r = 0.80, 0.79, respectively; p < 0.01), but no correlation was found between these parameters in HCM. Late-diastolic step (LDS) formation of the LAD flow velocity wave was observed in 68% of HCM, 20% of LVH(+)HT, but none of the LVH(-)HT patients. The A wave ratio of ACG was higher in patients with LDS than in those without (p < 0.01). The LDS occurred coincidently with the A wave of ACG.

CONCLUSIONS

The diastolic LAD flow velocity pattern in hypertrophied heart is characterized by slow acceleration and LDS formation, reflecting impaired relaxation and increased stiffness of the LV, respectively. These abnormalities correlate with the degree of hypertrophy in hypertensive heart, but do not correlate with that in HCM.

Non-invasive assessment of coronary flow and coronary flow reserve by transthoracic Doppler echocardiography: a magic tool for the real world

Transthoracic Doppler echocardiography, introduced in the echo-lab in recent last years, to measure coronary flow and coronary flow reserve, is a very attractive tool, totally non-invasive, and easily available at bedside. This review summarizes the actual possibilities of this tool, its multiple potential clinical applications and diagnostic insights, and its arising prognosis value, in coronary artery disease as in various settings affecting the coronary microcirculation.

Magnetic resonance imaging of delayed enhancement in hypertrophic cardiomyopathy: relationship with left ventricular perfusion and contractile function

PURPOSE

The aim of the study was to analyze the relationship between myocardial delayed enhancement, first-pass perfusion, and contractile function in hypertrophic cardiomyopathy (HCM) patients, using MR.

METHODS

Fifty-three patients diagnosed with HCM were prospectively examined using a 1.5-T MR unit. Multiphase gradient-echo sequences were performed to study global left ventricular function, wall thickness, and left ventricular mass. Myocardial tissue tagging was conducted to evaluate contractile function. T1-weighted inversion-recovery sequences were obtained at rest to study myocardial contrast enhancement at first pass and delayed enhancement 10 minutes later.

RESULTS

Delayed enhancement found in 30 patients (56.6%) was most commonly seen in hypertrophic segments. Nine patients exhibited delayed enhancement in segments with normal wall thickness (<15 mm). Sixteen patients (30.1%) showed first-pass perfusion defects at rest, which were associated with significantly lower stroke volume (P<0.05) and lower cardiac output (P<0.01). The hypokinetic segments found in 16 patients (30.1%) were significantly thicker at end diastole (P<0.01). Delayed enhancement correlated positively with perfusion defects (r=0.5, P<0.01) and hypokinetic segments (r=0.3, P<0.05).

CONCLUSION

Delayed myocardial enhancement is most commonly found in hypertrophic segments but also can be seen in segments with normal wall thickness. Perfusion defects at rest and impaired contractile function are related abnormalities with delayed myocardial enhancement. Further studies are necessary to assess the role of myocardial tagging, first-pass perfusion, and delayed enhancement in risk stratification for patients with HCM.

Comparison of diastolic septal perforator flow velocities in hypertrophic cardiomyopathy versus hypertensive left ventricular hypertrophy

In this study, we measured diastolic septal perforator flow velocities by Doppler transthoracic echocardiography (TTE) in patients with hypertrophic cardiomyopathy (HCM). Using color-guided pulsed Doppler TTE, septal perforator flow velocity recordings were attempted in 69 patients and successfully recorded in 47 (68%). First, we compared 14 patients with HCM to 12 controls and to 11 patients with hypertension with left ventricular hypertrophy. Next, in 10 additional patients with HCM, we compared the septal velocities with the epicardial left anterior descending artery (LAD) velocities recorded during the same TTE study. In the patients with HCM, the peak septal diastolic velocities were twice that of the normal controls (88 +/- 40 vs 41 +/- 13 cm/s) and also higher than in hypertensive left ventricular hypertrophy (51 +/- 18 cm/s, p < 0.0001). All 10 patients with HCM showed a step-up of peak diastolic velocity from the LAD to the septal perforator from 41 +/- 9 to 72 +/- 17 cm/s (p < 0.0001). Three patients with HCM had surgical septal myectomy. These patients had luminal narrowings of the small intramural arteries at histopathologic examination. In conclusion, pulsed Doppler measurement of septal perforator flow velocities is feasible. In HCM, the epicardial coronary arteries enlarge to accommodate increased flow, and diastolic velocity is normalized. In contrast, the increased velocities in the septal branches of patients with HCM are similar to those previously observed in tunnel-like obstructions. These findings suggest that in HCM, notwithstanding an increase in coronary flow, hemodynamically significant narrowings are present in the septal branches. Doppler TTE may become useful for evaluation of abnormal intramural coronary flow in HCM.

Comparison of Coronary Flow Velocities Between Patients with Obstructive and Nonobstructive Type Hypertrophic Cardiomyopathy: Noninvasive Assessment by Transthoracic Doppler Echocardiography

BACKGROUND

We aimed to compare coronary flow velocity (CFV) measurements of patients with nonobstructive (NHCM) and obstructive hypertrophic cardiomyopathy (HOCM) by using transthoracic Doppler echocardiography (TTDE).

METHODS AND RESULTS

In 11 patients with NHCM and 26 with HOCM, CFV in the distal left anterior descending (LAD) coronary was measured by TTDE (3.5 MHz) under the guidance of color Doppler flow mapping in addition to standard 2D and Doppler echocardiography. The results were compared with 24 normal participants who had no evidence of cardiac disease. Peak diastolic velocity of LAD was also higher in NHCM and HOCM than controls (52 +/- 14 cm/sec and 54 +/- 20 cm/sec vs 41 +/- 11 cm/sec, respectively, P < 0.01). The analysis of systolic velocities revealed abnormal flow patterns in 16 (61%) patients with HOCM (12 systolic-reversal flow and 4 no systolic flow) and 6 (54%) (5 reversal flow and 1 zero flow) patients with NHCM (-11 +/- 30 cm/sec and -13 +/- 38 cm/sec, vs 24 +/- 9 cm/sec, respectively, P < 0.001). Linear regression analysis demonstrated no correlation between intraventricular pressure gradient and coronary flow velocities in HOCM patients. However, there were significant positive and negative correlations between septal thickness and diastolic and systolic velocities, respectively (r = 0.50, P < 0.002, and r =-0.43, P < 0.005).

CONCLUSION

We conclude that the coronary flow velocity abnormalities are independent from the type of hypertrophic cardiomyopathy.

Transthoracic echocardiographic evaluation of coronary flow reserve in patients with hypertrophic cardiomyopathy

Recently, it has become possible to measure coronary flow reserve (CFR) non-invasively with transthoracic echocardiography (TTE). Twenty-one hypertrophic cardiomyopathy (HCMP) patients with asymmetric septal hypertrophy who had either not started medication or had stopped medication for at least 24 h were enrolled, along with 29 normal subjects. Mean diastolic coronary flow velocity (CFmv) and time velocity integral of diastolic coronary flow velocity (CFtvi) were measured at the distal left anterior descending artery with a 7 MHz transducer at the baseline and after dipyridamole infusion at a dose of 0.56 mg/kg. CFR was defined as the ratio of CFmv after dipyridamole over CFmv before dipyridamole. The baseline values for CFmv and CFtvi were significantly higher (0.40+/-0.09 vs. 0.31+/-0.06 m/s, p<0.001, 0.25+/-0.07 vs. 0.16+/-0.04 m, p<0.001, respectively), while that for CFR was significantly lower (2.01+/-0.42 vs. 3.06+/-0.39 m/s, p<0.001) in the HCMP patients, compared to the normal subjects. In the HCMP patients, CFR showed a moderate negative correlation with both baseline CFmv (r=-0.522, p=0.015) and baseline CFtvi (r=-0.495, p=0.034). Treadmill test was performed in 14 patients with Bruce protocol. CFR, baseline CFmv and baseline CFtvi did not correlate with maximal exercise time. In seven patients, the CFR measured after verapamil treatment was not significantly different from that measured before treatment. In conclusion, in patients with HCMP, CFR is probably reduced due to the recruitment of vasodilatory capacity at the resting state and this reduction is not directly related to reduced exercise capacity. Also, CFR is not affected by treatment with calcium antagonist.

Determinants of coronary flow abnormalities in obstructive type hypertrophic cardiomyopathy: noninvasive assessment by transthoracic Doppler echocardiography

We aimed to visualize the coronary flow velocities (CFV) of patients with hypertrophic obstructive cardiomyopathy by using transthoracic Doppler echocardiography, and to determine the relationship between abnormal CFV patterns and conventional echocardiography indices. Guided by 2-dimensional echocardiography and Doppler color flow mapping, CFV in the distal left anterior descending coronary artery were measured in 21 patients with hypertrophic obstructive cardiomyopathy using a 3.5-MHz transducer. The results were compared with those of 18 control subjects. Abnormal systolic flow patterns were observed in 15 (71%) patients (11 systolic-reversal flow and 4 no systolic flow). For patients and control subjects, peak diastolic velocity and velocity-time integral obtained from distal left anterior descending coronary artery were higher (63 +/- 21 cm/s and 18.5 +/- 4 cm vs 41 +/- 11 cm/s and 14.2 +/- 5 cm, respectively; P <.01 for both) whereas peak systolic velocity and velocity-time integral were significantly lower (-17 +/- 10 cm/s and 4.5 +/- 6 cm vs 24 +/- 9 cm/s and 9.5 +/- 4 cm, respectively; P <.001 for both). Significant positive and negative correlations between diastolic CFV and septal thickness index (r = 0.79, P <.0001), and between systolic CFV and septal thickness index (r = -0.65, P <.005), have been observed. CFV abnormalities that could easily be recorded by a standard Doppler echocardiographic study seem to be related to septal thickness rather than the degree of obstruction in hypertrophic obstructive cardiomyopathy.

Demonstration of coronary artery flow using transthoracic Doppler echocardiography

Transthoracic Doppler echocardiography is emerging as a promising method for evaluating coronary artery disease. After a period of training, detection and measurement of distal left anterior descending coronary artery flow with transthoracic Doppler echocardiography is feasible in more than 90% of the patients. Using transthoracic Doppler echocardiography with a high-frequency transducer and special setting of low Nyquist limits, pathologic coronary flow dynamics can be demonstrated. Measurement of coronary flow reserve may impact diagnosis or clinical treatment in those: (1) with anginal chest pain and angiographically normal coronary arteries; (2) with intermediate-grade coronary obstruction where the physiologic significance is in doubt; and (3) who have had an attempt at revascularization and the effectiveness of the therapy is uncertain.

Transthoracic Doppler echocardiography - noninvasive diagnostic window for coronary flow reserve assessment

This review focuses on transthoracic Doppler echocardiography as noninvasive method used to assess coronary flow reserve (CFR) in a wide spectrum of clinical settings. Transthoracic Doppler echocardiography is rapidly gaining appreciation as popular tool to measure CFR both in stenosed and normal epicardial coronary arteries (predominantly in left anterior descending coronary artery). Post-stenotic CFR measurement is helpful in: functional assessment of moderate stenosis, detection of significant or critical stenosis, monitoring of restenosis after revascularization. In the absence of stenosis in the epicardial coronary artery, decreased CFR enable to detect impaired microvascular vasodilatation in: reperfused myocardial infarct, arterial hypertension with or without left ventricular hypertrophy, diabetes mellitus, hypercholesterolemia, syndrome X, hypertrophic cardiomyopathy. In these diseases, noninvasive transthoracic Doppler echocardiography allows for serial CFR evaluations to explore the effect of various pharmacological therapies.

Blood flow in the left anterior descending coronary artery in children with ventricular septal defect

High-frequency echocardiography offers a noninvasive approach for imaging left anterior descending coronary artery (LAD) blood flow from a transthoracic window. The purpose of this study was to assess the effects of left ventricular (LV) volume overload on LAD flow in pediatric patients with ventricular septal defect (VSD). The study subjects consisted of 38 children with VSD and 15 healthy children. LV mass, LAD diameter, and LAD flow were measured by using transthoracic echocardiography, then LAD diameter and LV mass were indexed for body surface area. Pulmonary to systemic flow ratios (Qp/Qs) were obtained by cardiac catheterization. The Qp/Qs ratios ranged from 1.2 to 3.1 (mean 2.1 +/- 0.5). The mean LAD flow velocities, flow velocity integrals, and flow volumes were significantly higher in the patients than in the control subjects. LAD flow velocity and flow volume showed significant positive correlations with Qp/Qs, LV mass, and LV end-diastolic volume. Stepwise regression analysis revealed that Qp/Qs was the most important determinant of both LAD flow velocity (r(2) = 0.45, P < .0001) and LAD flow volume (r(2) = 0.44, P < .0001). The ratios of LAD flow volume to LV mass did not differ between the 2 groups. In 8 patients who underwent surgical treatment, LAD flow velocity, flow velocity integral, and flow volume decreased significantly after surgery. The current results suggest that patients with VSD have a higher resting coronary blood flow, and that LAD flow pattern is dependent on LV volume overload and changes after surgery.

Verapamil improves the pacing-induced vasodilatation in symptomatic patients with hypertrophic cardiomyopathy

The purpose of the study was to assess the effect of verapamil on the response of diastolic coronary flow velocity and coronary vascular resistance to pacing in symptomatic patients with hypertrophic cardiomyopathy. In 14 patients with hypertrophic cardiomyopathy, the coronary flow velocity was detected in the left anterior descending coronary artery using transthoracic Doppler echocardiography. The peak diastolic coronary flow velocity and coronary vascular resistance was measured at baseline and during pacing. Changes of these parameters induced by the pacing (expressed as the percentage of baseline values) were compared on verapamil treatment and after verapamil withdrawal. The same measurements were obtained in ten control subjects. The results show that, in hypertrophic cardiomyopathy patients, increase in coronary flow velocity during pacing was significantly higher on than off verapamil therapy (64.8+/-32.5 vs. 41.1+/-21.3%, P<0.05). In control subjects, pacing-induced increase in coronary flow velocity was comparable to changes in coronary flow velocity in hypertrophic cardiomyopathy patients receiving verapamil (80.2+/-18.4 vs. 64.8+/-32.5%, P>0.05). After verapamil withdrawal in hypertrophic cardiomyopathy patients, coronary flow velocity increase during pacing was significantly lower than in control subjects (41.1+/-21.3 vs. 80.2+/-18.4%, P<0.05). During pacing the coronary vascular resistance decreased more on verapamil than after drug withdrawal (-34.7+/-11.7 vs. -24.6+/-12.9%, P<0.05). In control subjects the coronary vascular resistance decreased during pacing -38.6+/-6.3% to similar extent as in hypertrophic cardiomyopathy patients on verapamil. We can conclude that endothelium-dependent vasodilatation during pacing was impaired in symptomatic patients with hypertrophic cardiomyopathy. Verapamil treatment was able to restore adequate vasodilator response to pacing stress.

Systolic compression of epicardial coronary and intramural arteries in children with hypertrophic cardiomyopathy

It has been suggested that systolic compression of epicardial coronary arteries is an important cause of myocardial ischemia and sudden death in children with hypertrophic cardiomyopathy. We examined the associations between sudden death, systolic coronary compression of intra- and epicardial arteries, myocardial perfusion abnormalities, and severity of hypertrophy in children with hypertrophic cardiomyopathy. We reviewed the angiograms from 57 children with hypertrophic cardiomyopathy for the presence of coronary and septal artery compression; coronary compression was present in 23 (40%). The left anterior descending artery was most often affected, and multiple sites were found in 4 children. Myocardial perfusion abnormalities were more frequently present in children with coronary compression than in those without (94% vs 47%, P = 0.002). Coronary compression was also associated with more severe septal hypertrophy and greater left ventricular outflow gradient. Septal branch compression was present in 65% of the children and was significantly associated with coronary compression, severity of septal hypertrophy, and outflow obstruction. Multivariate analysis showed that septal thickness and septal branch compression, but not coronary compression, were independent predictors of perfusion abnormalities. Coronary compression was not associated with symptom severity, ventricular tachycardia, or a worse prognosis. We conclude that compression of coronary arteries and their septal branches is common in children with hypertrophic cardiomyopathy and is related to the magnitude of left ventricular hypertrophy. Our findings suggest that coronary compression does not make an important contribution to myocardial ischemia in hypertrophic cardiomyopathy; however, left ventricular hypertrophy and compression of intramural arteries may contribute significantly.

Left anterior descending coronary artery flow and its relation to age in children

Recent advances in Doppler and color echocardiographic techniques enable coronary flow dynamics to be estimated even in children. To assess quantitatively left anterior descending coronary artery (LAD) volumetric flow and to determine its relation to age and left ventricular (LV) mass, healthy children participated in a study that used high-frequency transthoracic echocardiography. We also studied whether Doppler echocardiography can reliably measure LAD flow in a clinical setting. In 57 healthy children, 2-dimensional echocardiography was used to measure the diameter and cross-sectional area of the LAD and LV mass. LAD peak flow velocity, flow velocity integral, and flow volume were measured by Doppler echocardiography. We then calculated the ratio of LAD cross-sectional area to LV mass and the ratio of LAD flow volume to LV mass. In 12 patients with Kawasaki disease, LAD flow velocity and flow velocity integral were measured by Doppler echocardiography at the time of Doppler guide wire examination. There were significant correlations between echocardiographic and Doppler guide wire methods for flow velocity and flow velocity integral (r = 0.77 and 0.83, P <.01, respectively). The LAD flow velocity decreased significantly with age (r = -0.43, P <.01). The LAD flow volume per minute increased significantly with age (r = 0.55, P <.01). However, LAD flow volume/LV mass ratio in younger infants was high and decreased significantly with age (r = -0.66, P <.01). This study shows that LAD flow patterns can be reliably assessed by transthoracic Doppler echocardiography in the majority of pediatric subjects. In the current study, the LAD flow velocity and the ratio of LAD flow volume to LV mass in infants was high and decreased with age, suggesting high myocardial perfusion. High LAD peak velocity in infants may be related with high resting coronary flow. Age-related changes in the LAD flow characteristics must be taken into consideration in the study of the coronary circulation in children.

Myocardial bridging does not predict sudden death in children with hypertrophic cardiomyopathy but is associated with more severe cardiac disease

OBJECTIVES

We sought to examine the association between systolic compression of sections of epicardial coronary vessels (myocardial bridging) with myocardial perfusion abnormalities and clinical outcome in children with hypertrophic cardiomyopathy (HCM).

BACKGROUND

It has recently been suggested that myocardial bridging is an important cause of myocardial ischemia and sudden death in children with HCM.

METHODS

Angiograms from 57 children with HCM were reviewed for the presence of bridging (50% or more maximum systolic arterial compression). QT interval indices, echocardiographic and cardiac catheterization findings, treadmill exercise tests, exercise thallium scintigraphy, Holter monitoring and electrophysiologic study findings were compared in children with and without bridging. The findings were also related to the presence or absence of compression of septal branches of the left anterior descending artery (LAD).

RESULTS

Bridging was present in 23 (40%) of the children. Multiple coronary arteries were involved in four children. Bridging involved the LAD in 16 of 28 (57%) affected vessels. Myocardial perfusion abnormalities were present in 14 of 30 (47%) children without bridging and in 17 of 22 (94%) children with bridging, p = 0.002. However, bridging was associated with more severe septal hypertrophy (19+/-8 mm vs. 28+/-8 mm, p < 0.001), a higher septum:posterior wall thickness ratio (2.7+/-1.2 vs. 1.8+/-0.9, p < 0.001), and higher left ventricle (LV) outflow gradient (45+/-37 mm Hg vs. 16+/-28 mm Hg, p = 0.002). Compression of septal LAD branches was present in 37 (65%) of the children and was significantly associated with bridging, severity of LV hypertrophy and outflow obstruction. Multivariate analysis demonstrated that LV septal thickness and septal branch compression, and not bridging, were independent predictors of thallium perfusion abnormalities. There was a 90% power at 5% significance to detect an effect of bridging on thallium abnormalities at an odds ratio of 3. Bridging was also not associated with significantly greater symptoms, increased QT and QTc intervals and QTc dispersion, ventricular tachycardia on Holter or induced at EP study, or a worse prognosis.

CONCLUSIONS

Bridging and compression of septal branches of the LAD are common in HCM children and are related to magnitude of LV hypertrophy. Left ventricular hypertrophy and compression of intramyocardial branches of the epicardial coronary arteries may contribute to myocardial perfusion abnormalities. Our findings suggest that bridging does not result in myocardial ischemia and may not cause arrhythmias or sudden death in HCM children.

Coronary flow abnormalities in neonates with aortic stenosis

Left coronary artery flow velocities in neonates were determined noninvasively with transthoracic pulsed wave Doppler ultrasonography. In normal subjects (n = 30) there was diastolic flow predominance with median (range) peak flow velocity in diastole, 23.8 cm/s (12.7 to 51.3 cm/s), and median peak flow velocity in systole, 12.7 cm/s (7.8 to 35.0 cm/s). In 3 neonates with severe aortic stenosis, retrograde left coronary flow throughout systole was observed before surgery. In these patients there was forward systolic flow 4 to 8 days after successful surgical valvulotomy was performed.

Value of transthoracic echocardiography for the detection of high-grade coronary artery stenosis: prospective evaluation in 50 consecutive patients scheduled for coronary angiography

We prospectively evaluated the feasibility of direct, transthoracic evaluation of coronary arteries to diagnose flow-limiting lesions. Second harmonic mode in B-mode and fundamental mode for Doppler examinations was used. A stenosis was diagnosed when maximal flow velocity at least doubled in comparison with that of the adjacent segment or when local velocity was at least 2 m/s. Of the left anterior descending coronary artery segments assessed, 34 were proximal, 35 middle, and 34 distal segments. The corresponding figures for circumflex coronary artery segments were 17 proximal and 11 middle segments and for the right coronary artery, 14 proximal and 15 distal segments. No distal circumflex and only 1 mid right coronary artery segment was visualized. Twenty-eight stenoses were diagnosed. Specificity for stenosis detection was 96% to 100% and sensitivity was 62% to 66%. Echo-cardiography was unable to document occlusions. Transthoracic echocardiography allows for coronary artery assessment in a significant portion of patients scheduled for coronary angiography. It may be used to document the presence of coronary artery stenosis. With further technologic improvements, transthoracic echocardiography could enable the monitoring of the restenosis process after percutaneous transluminal coronary angioplasty/stent intervention and coronary artery luminal narrowing after heart transplantation.

Exercise-induced ST-segment depression and systolic dysfunction in patients with nonobstructive hypertrophic cardiomyopathy

BACKGROUND

ST-segment depression is common in patients with hypertrophic cardiomyopathy (HCM). However, it is not clear whether exercise-induced ST-segment depression in patients with HCM and patent coronary arteries is associated with changes in left ventricular function.

METHODS

Left ventricular function was continuously evaluated in 53 patients with nonobstructive HCM during supine ergometer exercise with a radionuclide ventricular function monitor equipped with a cadmium telluride detector. On the basis of the ST-segment changes during exercise, the patients were divided into 2 groups: group N had no ST-segment depression, and group D had >/=0.1 mV ST-segment depression.

RESULTS

Exercise duration, blood pressure, heart rate, and rate-pressure product during exercise did not differ between the 2 groups. End-diastolic volume at rest and at peak exercise did not differ between groups D and N. In contrast, the end-systolic volume in group N decreased during exercise, whereas in group D it increased. As a result, the left ventricular ejection fraction in group D decreased from 70% +/- 7% to 59% +/- 15% (P <.0001), whereas ejection fraction in group N increased from 65% +/- 8% to 71% +/- 11% (P =.0002). There was a strong correlation between exercise-induced ST-segment depression and changes in ejection fraction from rest to peak exercise (P <.0001).

CONCLUSIONS

These results suggest that the exercise-induced ST-segment depression seen in patients with nonobstructive HCM is associated with systolic dysfunction during exercise.

Effect of verapamil on systolic and diastolic coronary blood flow velocity in asymptomatic and mildly symptomatic patients with hypertrophic cardiomyopathy

OBJECTIVE

To assess non-invasively the effect of verapamil treatment on coronary blood flow velocity in asymptomatic and mildly symptomatic patients with hypertrophic cardiomyopathy.

DESIGN

High frequency transthoracic Doppler echocardiography was used to compare resting phasic coronary blood flow velocity before and after a one month period of verapamil treatment in 17 patients (14 men and three women) with non-obstructive hypertrophic cardiomyopathy. Eighteen healthy subjects formed an age and sex matched control group. Systolic and diastolic coronary blood flow velocity was measured in the distal portion of left anterior descending coronary artery using high frequency transthoracic Doppler echocardiography. Blood flow velocity before and after verapamil was compared in the patients with cardiomyopathy and with the results in the control group.

RESULTS

Compared with the controls, patients with hypertrophic cardiomyopathy had increased diastolic coronary blood flow velocity (41.8 (8.1) v 59.9 (21.9) cm/s, p < 0.01) and a lower mean systolic coronary blood flow velocity (18.7 (10.8) v -11.2 (27.5) cm/s, p < 0. 01) before verapamil treatment. A backward pattern of systolic flow, manifested by negative values of coronary blood flow velocity, was recorded in eight of the patients, while no negative values were found in the controls. After verapamil treatment the retrograde systolic blood flow was restored to an anterograde pattern in only one patient. The mean value of systolic coronary blood flow velocity did not change significantly and remained lower than the systolic forward flow velocity in the controls (-3.6 (31.8) v 18.7 (10.8) cm/s, p < 0.05). However, diastolic coronary blood flow velocity decreased significantly after verapamil (59.9 (21.9) v 50.7 (19.5) cm/s p < 0.05), reaching a level comparable with that in the controls (50.7 (19.5) v 41.8 (8.1) cm/s, p > 0.05).

CONCLUSIONS

In contrast to healthy subjects, in non-obstructive hypertrophic cardiomyopathy the systolic pattern of coronary blood flow was heterogeneous (both retrograde and anterograde), and diastolic coronary blood flow velocity was abnormally increased, despite a lack of significant symptoms. Verapamil treatment did not restore the forward pattern of systolic blood flow but decreased diastolic blood flow velocity to a level comparable with that in healthy subjects.

Noninvasive assessment of coronary flow velocity and coronary flow velocity reserve in the left anterior descending coronary artery by Doppler echocardiography: comparison with invasive technique

OBJECTIVES

The purpose of this study was to evaluate whether transthoracic Doppler echocardiography (TTDE) can reliably measure coronary flow velocity (CFV) and coronary flow velocity reserve (CFVR) in the left anterior descending coronary artery (LAD) in the clinical setting.

BACKGROUND

Coronary flow velocity measurement has provided useful clinical and physiologic information. Advancement in TTDE provides noninvasive measurement of CFV and CFVR in the distal LAD.

METHODS

In 23 patients, CFV in the distal LAD was measured by TTDE (5 or 3.5 MHz) under the guidance of color Doppler flow mapping at the time of Doppler guide wire (DGW) examination. Coronary flow velocity in the distal LAD were measured at baseline and hyperemic conditions (intravenous administration of adenosine 0.14 mg/kg/min) by both TTDE and DGW techniques. Coronary flow velocity reserve was defined as the ratio of peak hyperemic to basal averaged peak velocity in the distal LAD.

RESULTS

Clear envelopes of basal and hyperemic CFV in the distal LAD were obtained in 18 (78%) of 23 study patients by TTDE. There were excellent correlations between TTDE and DGW methods for the measurements of CFV (averaged peak velocity: r=0.97, y=0.94x + 0.40; averaged diastolic peak velocity: r=0.97, y=0.94x + 0.69; systolic peak velocities: r=0.97, y=0.91x + 0.87; diastolic peak velocity: r=0.98, y=0.95x + 1.10). Coronary flow velocity reserve from TTDE correlated highly with those from DGW examinations (r=0.94, y=0.95x + 0.21).

CONCLUSIONS

Noninvasive measurement of CFV and CFVR in the distal LAD using TTDE accurately reflects invasive measurement of CFV and CFVR by DGW method.

Transthoracic Doppler echocardiography of normally originating coronary arteries in children

Transthoracic Doppler color flow and spectral velocity patterns of normal coronary arteries in children have not been well studied. We designed this study to evaluate coronary artery flow velocity characteristics in normal and hypertrophied hearts. Sixty-eight children with optimal two-dimensional echocardiographic images of the left coronary artery (LCA) and right coronary artery (RCA) were prospectively studied. The heart was normal in 45 children, and 23 had left and/or right ventricular hypertrophy assessed by echocardiography (mean age 5.8 versus 5.2 years, p = NS). Color flow signals were detected in the LCA in 63(92%) of the 68 children studied, and pulsed Doppler spectral waveforms were recorded in 47 (69%). The latter were recorded in 26 (58%) of 45 normal children and in 21 (91%) of 23 children with left ventricular hypertrophy. Diastolic RCA flow signals were detected mostly in those with right ventricular hypertrophy (10 of 10). Higher levels of LCA maximum diastolic velocity (42 +/- 23 versus 24 +/- 6 cm/sec, p = 0.0004), increased diastolic flow (16 +/- 15 versus 6 +/- 4 ml/min, p = 0.01), and delayed time to peak diastolic velocity expressed as a percentage of diastolic spectral duration (38% +/- 14% versus 20% +/- 8%, p = 0.0001) were observed in children with left ventricular hypertrophy than in those in normal children. A strong correlation was present between Doppler-derived LCA flow and left ventricular mass/m2 (r = 0.7, p = 0.001). In normal hearts, LCA spectral velocity pattern did not change with increasing age, but the time velocity integral became progressively larger, resulting in a strong correlation with weight (p < 0.001, r = 0.78). This study demonstrates (1) LCA flow signals can be detected and quantitated in the majority of children with and those without left ventricular hypertrophy. (2) Left ventricular hypertrophy is associated with increased LCA flow, higher diastolic velocity, and delayed peak diastolic velocity. (3) RCA flow signals are mostly detected when there is right ventricular hypertrophy. Studies on larger groups of patients are needed to further confirm our observations and to enhance understanding of coronary artery flow reserve.

[Methods for coronary functional assessment]

Functional evaluation of coronary vasomotion encompasses the assessment of dynamic changes in coronary lumen, vessel wall, blood flow, intracoronary pressure and myocardial perfusion in response to specific pharmacologic stimuli. These parameters are obtained to characterize mechanisms of physiologic regulation and to evaluate pathophysiologic processes and potential therapeutic strategies, especially with regard to the development of coronary atherosclerosis. To this end, a variety of direct (invasive) and indirect (non-invasive) diagnostic tools are employed. Among the invasive methods are registration of intracoronary Doppler flow, coronary pressure measurements, quantitative coronary angiography and intravascular ultrasound. The non-invasive modalities consist of coronary Doppler echocardiography, positron emission tomography, myocardial scintigraphy and magnetic resonance imaging. Because of the different technical and physiological principles involved, these methods are complementary by providing independent access to different aspects. The combined invasive functional testing as employed in the cardiac catheterization laboratory allows for a simultaneous synopsis of high-resolution coronary imaging and direct measurement of physiologic parameters during local application of defined pharmacologically active substances. However, the demands in terms of equipment, time and operator skills are high and limit this combined invasive approach to specialized centers. Besides these research purposes, a number of functional methods has entered the clinical arena. They are employed to evaluate the hemodynamic significance of coronary lesions and to assess functional outcome of therapeutic interventions in the catheterization laboratory. The underlying principles and applications of the different methods are described and an overview of selected results is presented.