Skip to main content
Advertisement
Browse Subject Areas
?

Click through the PLOS taxonomy to find articles in your field.

For more information about PLOS Subject Areas, click here.

  • Loading metrics

Delayed blood pressure recovery after exercise stress test is associated with autonomic dysfunction and pulse pressure in a middle-aged healthy group

  • Hancheol Lee ,

    Contributed equally to this work with: Hancheol Lee, Hyeongsoo Kim

    Roles Data curation, Formal analysis, Investigation, Methodology, Project administration, Resources, Writing – original draft, Writing – review & editing

    Affiliation Division of Cardiology, National Health Insurance Service Ilsan Hospital, Goyang, Republic of Korea

  • Hyeongsoo Kim ,

    Contributed equally to this work with: Hancheol Lee, Hyeongsoo Kim

    Roles Data curation, Formal analysis, Funding acquisition, Investigation, Methodology

    Affiliation Division of Cardiology, National Health Insurance Service Ilsan Hospital, Goyang, Republic of Korea

  • Seungjin Oh,

    Roles Software, Validation, Visualization

    Affiliation Division of Cardiology, National Health Insurance Service Ilsan Hospital, Goyang, Republic of Korea

  • Jong-Kwan Park,

    Roles Resources, Supervision

    Affiliation Division of Cardiology, National Health Insurance Service Ilsan Hospital, Goyang, Republic of Korea

  • Ji-Yong Jang,

    Roles Conceptualization, Data curation, Methodology

    Affiliation Division of Cardiology, National Health Insurance Service Ilsan Hospital, Goyang, Republic of Korea

  • Kyeong-Hyeon Chun,

    Roles Resources, Validation

    Affiliation Division of Cardiology, National Health Insurance Service Ilsan Hospital, Goyang, Republic of Korea

  • Se-Jung Yoon

    Roles Conceptualization, Investigation, Supervision, Validation, Writing – review & editing

    drpuoohsjy@gmail.com

    Affiliation Division of Cardiology, National Health Insurance Service Ilsan Hospital, Goyang, Republic of Korea

Abstract

Background

Delayed heart rate (HR) and blood pressure recovery after exercise test is known as the reliable indexes of autonomic dysfunction. Here we tried to evaluate the serial changes in various indicators during exercise test and correlations with recovery of HR and blood pressure in a normotensive healthy middle-aged group.

Methods

A total of 122 patients without hypertension or diabetes was enrolled (mean age, 55.6 ± 11.0; male, 56.6%; mean blood pressure, 124.8 ± 16.6 / 81.5 ± 9.6 mmHg). Treadmill test was performed for evaluation of chest pain. Patients with coronary artery disease, positive treadmill test result, left ventricular dysfunction or renal failure were excluded. Heart rate recovery was calculated by subtracting the HR in the first or second minute of recovery period from the HR of peak exercise (HRR1 or HRR2). Systolic blood pressure in the 4th minute of recovery stage (SBPR4) was used to show delayed blood pressure recovery.

Results

Metabolic equivalents (METs) and HR in stage 2 to 4 were significantly correlated with both HRR1 and HRR2. Multiple regression analysis of HRR revealed significant correlation of METs and SBPR4. SBPR4 was significantly correlated with both HRR1 and HRR2 (HRR1, r = -0.376, p<0.001; HRR2, r = -0.244, p = 0.008) as well as SBP in the baseline to stage 3 and pulse pressure (r = 0.406, p<0.001).

Conclusions

Delayed BP recovery after peak exercise test revealed significant association with autonomic dysfunction and increased pulse pressure in normotensive middle-aged healthy group. It can be a simple and useful marker of autonomic dysfunction and arterial stiffness.

1. Introduction

Exercise stress test is easy to perform and useful physiological test. It has the advantage of being able to check the serial changes of vital signs during gradual loading.

Delayed heart rate recovery (HRR) was well known as the difference between the heart rate of peak exercise and a specific stage during the recovery time in a patient undergoing a maximal stress test. It has been revealed to be associated with the balance of sympathetic and parasympathetic tonus. HRR is a reflection of vagal reactivation and impaired HRR is considered to indicate a blunted reactivation of vagal tone [13].

HRR abnormalities are often seen in patients with metabolic disorders, including cardiovascular disease, fatty liver, diabetes and prehypertension [48]. Blunted HRR has been reported the association with chronic heart failure and new-onset atrial fibrillation [9, 10]. It has been revealed as an independent predictor of mortality and adverse outcomes [1118]. Mahfouz et al. [19], suggested that abnormal HRR and delayed systolic blood pressure recovery after exercise were correlated with impaired endothelial function and diastolic dysfunction in prediabetics.

Systolic blood pressure at recovery stage (SBPR) immediately after exercise also has been found to have diagnostic value for coronary artery disease and myocardial perfusion abnormalities [20, 21]. Although not as well known as HRR, it was also known to be affected by autonomic function [22, 23] and has been known to have a strong relationship with cardiovascular disease and overall mortality [2327]. To the best of our knowledge, no study has been found on the correlation between the hemodynamic indices and autonomic nerve function at each stage in the exercise stress test. Moreover, association of SBPR with HRR and other serial exercise indices has not been identified in peak exercise test of middle-aged healthy non-hypertensives. Here we tried to evaluate the serial changes in various indicators and correlations among them including HRR and SBPR of peak exercise test in a normotensive healthy middle-aged group.

2. Materials and methods

2.1. Study participants

The study population consisted of individuals referred for treadmill exercise test for the evaluation of chest pain between January 2014 and December 2017. Patients under 18 years of age, severe obesity (BMI ≥ 35 Kg/m2), positive treadmill test result, medical history of hypertension, diabetes mellitus, dyslipidemia, any cardiovascular disease, left ventricular dysfunction, valvular heart disease, atrial fibrillation or renal failure were excluded.

2.2. Protocol of the exercise stress test

The patients underwent a standard maximal graded exercise treadmill test according to the standard Bruce protocol with a T2100-ST2 Treadmill system (GE Inc., Boston, MA). Continuous 12-lead electrocardiographic monitoring was performed throughout testing. The Tango exercise BP monitoring device (SunTech Medical, Morrisville, NC) was used to automatically measure each subject’s BP and HR before and at the second minute of each stage of the exercise. The participants exercised until the HR achieved was >95% of estimated maximal HR (220 –age). The patients continued to walk for 30 seconds at a speed of 1.5 mph during the recovery period, after which they sat down with continued BP and HR

Monitoring [19, 28]. HRR values were calculated by subtracting the HR at the first, second and fourth minute of the recovery period from the HR reached at peak exercise. The exercise capacity was calculated as total metabolic equivalent units (METs) achieved at peak exercise.

2.3. Statistical analysis

All analyses were made using the SPSS 20.0 for Windows software package (SPSS Inc., Chicago, IL, USA). Continuous variables were presented as a mean ± standard deviation and categorical variables as a percentage of the group total. Pearson’s correlation analyses were performed to determine the association of HRR and SBP in the 4th minute of recovery stage (SBPR4) with other indicators of exercise test. A stepwise, multiple regression analysis was used to identify significant determinants of HRR in the first and second minute of recovery stage, which included variables that correlated with a P-value of less than 0.1 in the Pearson’s correlation analysis. A P-value of less than 0.05 was considered significant.

3. Results

3.1. Baseline characteristics and exercise data of treadmill test

A total of 122 patients without diabetes or hypertension were enrolled (mean age, 55.6 ± 11.0; male, 56.6%; mean baseline blood pressure, 124.8 ± 16.6 / 81.5 ± 9.6 mmHg). Mean body mass index (BMI) was under obesity (25.0 ± 4.6 Kg/m2) and exercise capacity is satisfactory (11.6 ± 1.9 metabolic equivalent (METs)) (Table 1).

thumbnail
Table 1. Baseline characteristics and exercise data of treadmill test.

https://doi.org/10.1371/journal.pone.0285961.t001

3.2. Correlation of HRR with other hemodynamic index

Baseline BP, baseline HR, peak BP were not significantly correlated with HRR in the first and second minute of recovery stage (HRR1 and HRR2). However age, metabolic equivalents (METs), HR in stage 2 to 4 and SBPR4 were significantly correlated with both HRR1 and HRR2 (HRR1, r = 0.248, p = 0.006; HRR2, r = 0.308, p = 0.001 with HR at stage 2) (Table 2). Multiple regression analysis of HRR1 and HRR2 revealed significant correlation with METs and SBPR4 (Table 3, Fig 1).

thumbnail
Fig 1. Correlation of HRR in the first minute of recovery stage with other basic and hemodynamic parameters.

Abbreviations. HRR1min, HRR in the first minute of recovery stage, METs, metabolic equivalents; recovery4min SBP, systolic blood pressure in the 4th minute of recovery stage; HR, heart rate. *p < 0.05.

https://doi.org/10.1371/journal.pone.0285961.g001

thumbnail
Table 2. Correlation of HRR with other hemodynamic index.

https://doi.org/10.1371/journal.pone.0285961.t002

thumbnail
Table 3. Correlation of HRR with other basic and hemodynamic parameters.

https://doi.org/10.1371/journal.pone.0285961.t003

3.3. Correlation of BP at recovery stage with other hemodynamic index including HRR

SBPR4 revealed significant correlation with SBP at baseline, stage 1~3 each (r = 0.537, p<0.001 at baseline; r = 0.595, p<0.001 at stage 1; r = 0.575, p<0.001 at stage 2; r = 0.567, p<0.001 at stage 3). HR at recovery stage (1st and 2nd minute) (r = 0.205, p = 0.029 at 1st minute of recovery stage; r = 0.193, p = 0.040 at 2nd minute of recovery) and HRR (r = -0.376, p<0.001 HRR1; r = -0.244, p = 0.008 HRR2) were significantly correlated with SBPR4.

Pulse pressure was significantly correlated with SBPR4 (r = 0.406, p<0.001). On the contrary, DBP in the 4th minute of recovery stage showed significant correlation only with DBP at each stage (Table 4, Fig 2).

thumbnail
Fig 2. Correlation of SBP in the 4th minute of recovery stage with other basic and hemodynamic parameters.

Abbreviations. SBPrecovery4min, systolic blood pressure in the 4th minute of recovery stage; DBPrecovery4min, diastolic blood pressure in the 4th minute of recovery stage; HRR1,2min, HRR in the first and second minute of recovery stage. *p < 0.05.

https://doi.org/10.1371/journal.pone.0285961.g002

thumbnail
Table 4. Correlation of blood pressure in the 4th minute of recovery stage with other hemodynamic indexes.

https://doi.org/10.1371/journal.pone.0285961.t004

4. Discussion

In this study, we have performed the analysis in a middle-aged healthy group without medical history of hypertension or diabetes mellitus, who had good exercise capacity (mean exercise capacity of 11.6 and mean age of 55.6). We investigated variables associated with HRR, an indicator of autonomic nerve function, during normal exercise load tests and found that systolic blood pressure at recovery stage was significantly associated. And systolic blood pressure at recovery stage showed significant relevance to SBP at each stage, HRR and pulse pressure in middle-aged healthy group.

Based on these results, HRR gets blunted down as aging and decreased exercise intensity.

The increase in heart rate during exercise was significantly proportional to HRR and rapid decrease in heart rate during recovery showed significant negative correlation with HRR in this group. This indicates that HR, which rises high during exercise and rapidly decreases during recovery appears as desirable HRR and can represent good autonomic function.

We can also see that the better the HRR, the faster the SBPR stabilizes. It seems that the better the autonomic nerve functions, the faster the blood pressure and HR after exercise are stabilized due to harmonious reactivation of parasympathetic tone after peak exercise.

SBPR is analyzed to be significantly related to SBP before and during exercise. Additionally, arterial stiffness represented by pulse pressure showed a significant proportional relationship with SBPR in this study.

After exercise, HR and BP normally decrease to resting levels via reactivation of vagal tone and withdrawal of sympathetic neural drive in healthy persons [29]. The response of systolic blood pressure to exercise is influenced by two neurohormonal mechanisms. The first involves the parasympathetic and sympathetic efferent changes that result in a cardiovascular response to exercise. The other includes the autonomic efferent response due to intramuscular afferent receptors that are sensitive to the metabolites produced by skeletal muscle [23]. Arteriolar tone is also influenced by the release of these local factors, which include nitric oxide, adenosine, lactate, and the subsequent decline in pH associated with exercise [22].

Schwartz et al. have reported that increased vagal tone is associated with improved survival, emphasizing the importance of HRR as a prognostic marker [30]. SBPR immediately after exercise also has been found to have diagnostic value for coronary artery disease and myocardial perfusion abnormalities [20, 21, 25, 26] and it has revealed strong relationship with HRR, cardiac diastolic function, cardiovascular disease and overall mortality including sudden cardiac death [3, 19, 2327, 29, 31, 32].

A previous study showed similar results with ours. The positive correlation between HRR1 and decrease of systolic blood pressure at the first minute of the recovery stage in subjects without exaggerated blood pressure response to exercise (EBPR) was presented and the enrolled patients had similar characteristics with our study group without medical history of hypertension, diabetes mellitus, cardiovascular or other systemic disease [33].

In another study, SBPR1 and 2 values were observed to be significantly blunted in the metabolic syndrome group. They thought that autonomic and endothelial dysfunction, which has previously been well established in patients with metabolic syndrome, might play an essential role in these impaired SBPR values [3]. Kontsas et al. presented that delayed blood pressure response detected during recovery stage implied a reverse relationship with peripheral vascular resistance during exercise in treated hypertensives using pulse wave velocity (PWV) and blood pressure recovery ratio [29]. Recently significant association between HRR1 and augmentation index was reported, which demonstrated the correlation of HRR with arterial stiffness. In this data, we did not show significant correlation between HRR and pulse pressure, but between SBPR4 and pulse pressure [34].

SBPR4 has also been used as an important index in previous study that showed notable difference between two groups of HRR cutoff point of 18 beats per minute. However it was not revealed as a significant predictor of sudden cardiac death and cardiovascular mortality during a follow-up period of 47±13 months [35].

The SBPR decreases after exercise may be a reflection of a person’s level of physical activity and fitness. The more rapid decline indicates the higher level of physical fitness, and a greater decrease in SBP from peak exercise to the recovery may reflect good aerobic capacity [16, 23, 27]. Researches also showed age differences in SBPR after exercise with faster recovery of SBP in younger adults than older group [36].

To our knowledge, this is the first study to analyze several continuous and stepwise aerobic exercise indexes and find mutual correlation in the middle-aged healthy group including HRR, SBP in the recovery stage and arterial stiffness with pulse pressure. Delayed SBP recovery after peak exercise test revealed significant association with autonomic dysfunction and increased pulse pressure in this group. It can be a simple and useful marker of autonomic dysfunction and arterial stiffness in the middle-aged healthy group.

There were several limiting factors in our study. Although the research population has relatively homogeneous characteristics, this study is a small sized retrospective, single-center study and needs to be verified in various diseases and conditions. It can be better to be validated by larger, prospective, multicenter studies. Further limitations include a lack of analysis of cardiovascular events or occurrence of metabolic disorders through continuous tracking. Additionally, coronary artery disease is excluded but the patients were not performed any imaging study such as angiography or computed tomography but only treadmill test.

If a large-scale long-term follow-up study in patients with diabetes or metabolic syndrome can be conducted in the future, various promising analyses can be expected.

5. Conclusions

In summary, delayed SBP recovery after peak exercise test revealed significant association with reduced HRR and increased pulse pressure in this group. It can be a simple and useful marker of autonomic dysfunction and arterial stiffness in the middle-aged healthy group.

References

  1. 1. Arai Y, Saul JP, Albrecht P, Hartley LH, Lilly LS, Cohen RJ, et al. Modulation of cardiac autonomic activity during and immediately after exercise. Am J Physiol 1989; 256:132–141. pmid:2643348
  2. 2. Savin WM, Davidson DM, Haskell WL. Autonomic contribution to heart rate recovery from exercise in human. J Appl Physiol 1982; 53:1572–1575.
  3. 3. Alihanoglu YI, Yildiz BS, Kilic ID, Uludag B, Demirci EE, Zungur M, et al. Impaired systolic blood pressure recovery and heart rate recovery after graded exercise in patients with metabolic syndrome. Medicine (Baltimore) 2015; 94(2):e428. pmid:25590851
  4. 4. Cai S, Ou Z, Liu D, Liu L, Liu Y, Wu X, et al. Risk factors associated with liver steatosis and fibrosis in chronic hepatitis B patient with component of metabolic syndrome. United European Gastroenterol J 2018; 6:558–566. pmid:29881611
  5. 5. Li X, Wang Y, Mi X, Qiao Z, Liang Y. Impaired heart rate recovery as a predictor for poor health-related quality in patients with transient ischemic attack. Medicine (Baltimore) 2019; 98(34):e16938. pmid:31441885
  6. 6. Aneni E, Roberson LL, Shaharyar S, Blaha MJ, Agatston AA, Blumenthal RS, et al. Delayed heart rate recovery is strongly associated with early and late-stage prehypertension during exercise stress testing. Am J Hypertens 2014; 27(4):514–521. pmid:24042166
  7. 7. Yu TY, Hong WJ, Jin SM, Hur KY, Jee JH, Bae JC, et al. Delayed heart rate recovery after exercise predicts development of metabolic syndrome: A retrospective cohort study. J Diabetes Investig 2022; 13:167–176. pmid:34313016
  8. 8. Deniz F, Katircibasi MT, Pamukcu B, Binici S, Sanisoglu SY. Association of metabolic syndrome with impaired heart rate recovery and low exercise capacity in young male adults. Clin Endocrinol 2007; 66:218–223. pmid:17223991
  9. 9. Imai K, Sato H, Hori M, Kusuoka H, Ozaki H, Yokoyama H, et al. Vagally mediated heart rate recovery after exercise is accelerated in athletes but blunted in patients with chronic heart failure. J Am Coll Cardiol 1994; 24:1529–1535. pmid:7930286
  10. 10. Maddox TM, Ross C, Ho PM, Magid D, Rumsfeld JS. Impaired heart rate recovery is associated with new-onset atrial fibrillation: a prospective cohort study. BMC Cardiovasc Disord 2009; 12:11. pmid:19284627
  11. 11. Lachman S, Terbraak MS, Limpens J, Jorstad H, Lucas C, Scholte Op Reimer W, et al. The prognostic value of heart rate recovery in patients with coronary artery disease: a systematic review and meta-analysis. Am Heart J 2018; 199:163–169. pmid:29754656
  12. 12. Qiu S, Cai X, Sun Z, Li L, Zuegel M, Steinacker JM, et al. Heart rate recovery and risk of cardiovascular events and all-cause mortality: a meta-analysis of prospective cohort studies. J Am Heart Assoc 2017; 6:e005505. pmid:28487388
  13. 13. Sági B, Késői I, Vas T, Csiky B, Nagy J, Kovács T. The prognostic role of heart rate recovery after exercise and metabolic syndrome in IgA nephropathy. BMC Nephrology 2021; 22:390. pmid:34809611
  14. 14. Donnellan E, Wazni OM, Chung MK, Elshazly MB, Chung R, Taigen T, et al. Attenuated heart rate recovery is associated with higher arrhythmia recurrence and mortality following atrial fibrillation ablation. Europace 2021; 23:1063–1071. pmid:33463688
  15. 15. Yoon GS, Choi SH, Kwon SW, Park SD, Shin SH, Woo SI, et al. Correlation of heart rate recovery and heart rate variability with atrial fibrillation progression. J Int Med Res 2021; 49(11):3000605211057822. pmid:34791909
  16. 16. Rezende CF, Mancuzo EV, Corrêa RA. Heart rate recovery in 1 minute after the 6-minute walk test predicts adverse outcomes in pulmonary arterial hypertension. PLoS One 2022; 17(5):e0268839. pmid:35622825
  17. 17. Shetler K, Marcus R, Froelicher VF, Vora D, Kalisetti D, Prakash M et al. Heart rate recovery: validation and methodologic issues. J Am Coll Cardiol 2001; 38:1980–1987. pmid:11738304
  18. 18. Lauer MS. Is heart rate recovery a modifiable risk factor? J Cardiopulm Rehabil 2003; 23:88–89. pmid:12668928
  19. 19. Mahfouz RA, Dewedar A, Elawady W, Salem A, Goda M. Delayed blood pressure recovery ratio and its relation to endothelial function and left ventricular diastolic function in prediabetics. Echocardiography 2014; 31(7):858–864. pmid:24354400
  20. 20. McHam SA, Marwick TH, Pashkow FJ, Lauer MS. Delayed systolic blood pressure recovery after graded exercise: an independent correlate of angiographic coronary disease. J Am Coll Cardiol 1999; 34:754–759. pmid:10483957
  21. 21. Taylor AJ, Beller GA. Post-exercise systolic blood pressure response: association with the presence and extent of perfusion abnormalities on thallium-201 scintigraphy. Am Heart J 1995; 129:227–234. pmid:7832093
  22. 22. Kitaoka H, Takata J, Furuno T, Yamasaki F, Chikamori T, Doi YL. Delayed recovery of postexercise blood pressure in patients with chronic heart failure. Am J Cardiol 1997; 79:1701–1704. pmid:9202371
  23. 23. Ellis K, Pothier CE, Blackstone EH, Lauer MS. Is systolic blood pressure recovery after exercise a predictor of mortality? Am Heart J 2004; 147:287–292. pmid:14760327
  24. 24. Miyahara T, Yokota M, Iwase M, Watanabe M, Matsunami T, Koide M, et al. Mechanisms of abnormal postexercise systolic blood pressure response and its diagnostic value in patients with coronary artery disease. Am Heart J 1990; 120:40–49.
  25. 25. Tsuda M, Hatano K, Hayashi H, Yokota M, Hirai M, Saito H. Diagnostic value of postexercise systolic blood pressure response for detecting coronary artery disease in patients with or without Hypertension. Am Heart J 1993; 125:718–725. pmid:8438701
  26. 26. Yamaguchi M, Shimizu M, Ino H, Okeie K, Yasuda T, Fujino N, et al. Diagnostic usefulness of the post-exercise systolic blood pressure response for the detection of coronary artery disease in patients with diabetes mellitus. Jpn Circ J 2000; 64:949–952. pmid:11194289
  27. 27. Laukkanen JA, Kurl S, Salonen R, Lakka TA, Rauramaa R, Salonen JT. Systolic blood pressure during recovery from exercise and the risk of acute myocardial infarction in middle-aged men. Hypertension 2004; 44:820–825. pmid:15534077
  28. 28. Kim BJ, Jo EA, Im SI, Kim HS, Heo JH, Cho KI. Heart rate recovery and blood pressure response during exercise testing in patients with microvascular angina. Clin Hypertens 2019; 25:4. pmid:30867938
  29. 29. Kontsas K, Triantafyllidi H, Trivilou P, Ikonomidis I, Tzortzis S, Liazos I, et al. Delayed blood pressure recovery ratio might indicate increased arterial stiffness in hypertensive patients with reduced aerobic exercise capacity. Blood Press 2013; 22(5):290–296. pmid:23373532
  30. 30. Schwartz PJ, La Rovere MT, Vanoli E. Autonomic nervous system and sudden cardiac death: experimental basis and clinical observations for post-myocardial infarction risk stratification. Circulation 1992; 85:I77–I91.
  31. 31. Evrengül H, Yüksel S, Doğan M, Gürses D, Evrengül H. Deteriorated Systolic Blood Pressure Recovery and Heart Rate Recovery After Graded Exercise in Children With Familial Mediterranean Fever. Arch Rheumatol 2017; 32(3):244–249. pmid:30375532
  32. 32. Laukkanen JA, Willeit P, Kurl S, Mäkikallio TH, Savonen K, Ronkainen K, et al. Elevated systolic blood pressure during recovery from exercise and the risk of sudden cardiac death. J Hypertens. 2014 Mar; 32(3):659–666. pmid:24317550
  33. 33. Dogan U, Duzenli MA, Ozdemir K, Gok H. Blunted heart rate recovery is associated with exaggerated blood pressure response during exercise testing. Heart Vessels 2013; 28:750–756. pmid:23080287
  34. 34. Latchman PL, Yang Q, Kong L, Zhang H, Sebagisha J, De Meersman RE. Heart Rate Recovery, Central Systolic Pressure, and Augmentation Index in Young Healthy Individuals. Vasc Health Risk Manag 2022; 18:17–25. pmid:35173435
  35. 35. Nieminen T, Leino J, Maanoja J, Nikus K, Viik J, Lehtimäki T, et al. The prognostic value of haemodynamic parameters in the recovery phase of an exercise test. The Finnish Cardiovascular Study. Journal of Human Hypertension 2008; 22:537–543. pmid:18509348
  36. 36. Dimkpa U, Ugwu AC. Age-Related Differences in Systolic Blood Pressure Recovery after a Maximal-Effort Exercise Test in Non-Athletic Adults. Int J Exerc Sci 2008; 1(4):142–152. pmid:27182304